Reviews You Can Rely On

Best Base Layer for Men of 2021

Wake up and be awesome! The Patagonia Capilene Cool Lightweight is one...
Photo: Jill Rice
Thursday May 27, 2021
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For a decade, our team of experts has tested 40+ of the best base layers on the market. For 2021, we directly compare 16 of the most popular options side-by-side. From the ski slopes to sleeping out under the stars, our in-depth analysis combines laboratory-style testing with real-world adventure to break down the strengths and weaknesses of each of these products. Our comprehensive review also provides valuable buyer's advice, to empower you with the information to find the right choice for your needs and budget. Whether it's for the warm or cold season, a quality base layer is sure to keep you dry and comfortable, no matter where your next adventure takes you.

Related: Best Base Layer for Women

Top 16 Product Ratings

Displaying 6 - 10 of 16
 
Awards  Top Pick Award    
Price $109.00 at Backcountry$119.95 at Backcountry
Compare at 2 sellers
$95.00 at Backcountry
Compare at 3 sellers
$79.50 at REI$40 List
Check Price at REI
Overall Score
71
71
66
63
60
Star Rating
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Pros Durable, 4-season versatility, comfortable Merino-blendOdor resistance, NuYarn technology, thumb loops, all-day comfortComfortable, nice fit, breathable, versatile, quick to dry, odor resistantSuper comfortable, odor resistant, breathable, fun colors, wicks wellInexpensive, breathable, functional
Cons Expensive, specific fit, slow to dryExpensive, susceptible to abrasionExpensive, lack of durability, heavy when wetNot durable, loose fit thru torso, loses shape after consistent washing/dryingLack of durability, long dry times
Bottom Line Walking the line between light- and mid-weight, this technical Merino-blend skillfully adapts to a variety of environmentsInnovative fabric technology help this layer stand out for backcountry skiing use, offering a high-performance value that more than makes up for the investmentAlthough not an award winner, this 100% merino wool top does a great job balancing warmth with breathability to bring you a solid, year-round workhorseA super comfortable 100% merino wool midweight base layer that is warm enough for winter ventures but light enough to carry you through Spring and Fall outingsA simple, functional base layer with performance issues consistent with its price point
Rating Categories Norrona Wool Round Neck Black Diamond Solution 150 M... Icebreaker 200 Oasis REI Co-op Merino Midweight REI Co-op Lightweight Crew
Warmth (25%)  
7
7
7
7
7
Breathability (20%)
7
8
7
6
6
Comfort And Fit (20%)
7
8
7
6
6
Drying Speed (10%)
5
6
5
6
4
Durability (15%)
8
4
6
6
5
Layering Ability (10%)
8
9
6
6
7
Specs Norrona Wool Round... Black Diamond... Icebreaker 200 Oasis REI Co-op Merino... REI Co-op...
Material 89% merino wool, 11% polyamide NuYarn: 78% merino wool, 22% polyester 100% merino wool 100% merino wool 92% polyester, 8% spandex
Fabric Weight 170 g/m² 150 g/m² 200 g/m² 200 g/m² Not Listed
Weight (size M) 7.5 oz 6.5 oz 7.7 oz 8.5 oz 6.1 oz
Types available crew crew crew, short sleeve, half zip crew, 1/4 zip short sleeve, crew, 1/4 zip
Thumb Loops? No Yes No No No
Air Dry Test (minutes) 50 45 35 45 70
Fit Slim fit Slim fit Slim fit Slim fit Semi-fitted
Stitching Flatlock seams Flatlock seams Flatlock seams Flat seams Flatlock seams
Dryer safe? No No No Yes Yes
Shoulder top seams? No No No No No
Drop tail hem? No No Yes Yes Yes


Best Overall Midweight Base Layer


SmartWool Merino 250 Crew


78
OVERALL
SCORE
  • Warmth - 25% 9
  • Breathability - 20% 7
  • Comfort and Fit - 20% 9
  • Drying Speed - 10% 5
  • Durability - 15% 7
  • Layering Ability - 10% 8
Materials: 100% merino wool | Weight: 9.2 ounces (size Medium)
Cozy, plush feel
Impressive thermoregulation
Incredibly warm
Balance of style and versatility
Odor resistant
Easily stretches out between washes
Relatively heavy
Price

A top that is likely to earn its place as your go-to for all cold-weather activity, the SmartWool Merino 250 Crew continues to shine in this category. Not only does this top offer superior comfort next-to-skin, but it is remarkably versatile as a mid-layer. You can lean on the 100% merino wool weave for its excellent temperature regulation, moisture wicking capability, and all-natural antimicrobial qualities. We've worn it for days on end, both at home and out on multi-day backcountry trips. Unlike its synthetic competitors, it somehow manages to be very acceptable — stench-wise — after many days between washes. This layer performs well in a wide range of temperatures, allowing you to quickly transition from static cold to high-exertion, all while staying warm, dry, and comfortable.

As to be expected of natural fibers, this top will begin to slouch and sag a bit through consistent wear. And as is true of all merino tops we tested, including the Merino 250 Crew, special care with washing and drying should be taken to ensure the longevity of this layer. When the fabric becomes saturated — as with handwashing — this top is comparatively slow to dry. From the crag to the mountain and then back down for a night on the town, the SmartWool Merino 250 is comfortable and stylish enough to wear every day. It excels in practically any cool- or cold-weather activity, from resort skiing to winter alpine ascents to hanging on chilly mornings on desert climbing or rafting trips.

Read review: SmartWool Merino 250 Crew

Best Lightweight Base Layer


NW Alpine Spectra


75
OVERALL
SCORE
  • Warmth - 25% 5
  • Breathability - 20% 9
  • Comfort and Fit - 20% 8
  • Drying Speed - 10% 7
  • Durability - 15% 9
  • Layering Ability - 10% 8
Materials: 90% Polyester, 10% Spectra | Weight: 4.8 oz (size Medium)
Spectra fabric is the most durable on the market
Ultra-lightweight
Merino-like feel from a synthetic layer
Not very warm
Odor retention
Lack of articulation

Though the brand name and material may both be new to the scene, the two are working in conjunction to set a high bar when it comes to lightweight, technical clothing. The NW Alpine Spectra is just one piece in a line that is the first in the world to incorporate Spectra fiber — an innovative material that is engineered to be lighter and stronger than Kevlar. This highly technical, highly breathable ultra-lightweight layer is able to easily withstand normal abrasion, rips, and tears, yet it is as soft next-to-skin as merino wool. No longer do mountain athletes have to sacrifice durability to save weight, nor do they have to substitute comfort for performance.

Though it is a versatile, lightweight option, the Spectra won't provide you with any of the insulation you may need to make it through the coldest days of winter. Despite all of the advances this top is making in the world of base layers, it still falls victim to some common pitfalls of full-synthetics — even casual efforts leave this top smelling as if you just pushed for an FKT. So while you may find yourself washing this top more than usual, you can rest assured knowing that the Spectra Long Sleeve won't wear out quickly. This ultra-durable lightweight base is built for the rigors of rock climbing but does equally well as a trail running top, or for working hard in the skin track when backcountry skiing. If you're looking for a lightweight base layer, this is the best we've tested.

Read review: NW Alpine Spectra

Best Midweight Bang for Your Buck


Meriwool Midweight Thermal


73
OVERALL
SCORE
  • Warmth - 25% 8
  • Breathability - 20% 8
  • Comfort and Fit - 20% 7
  • Drying Speed - 10% 6
  • Durability - 15% 7
  • Layering Ability - 10% 6
Materials: 100% merino wool | Weight: 9.8 oz (size Medium)
Affordable
Balances warmth and breathability
Stylish
Not as warm as we expected
Slightly itchy
Shoulder top seams

You may be surprised to discover that you actually don't have to pay an arm and a leg for a superb Merino wool top. The Meriwool Midweight Thermal offers near top-quality performance at a fraction of the cost of most of the 100% Merino tops we tested. Even though it is firmly in the midweight category, the extra-fine spun wool used to create this layer is more breathable than other directly comparable models, making it a great option for folks engaged in high-output activities like ski touring. Couple that with a slim, stylish fit, and you have a layer you can take from the mountain straight to après-ski.

The benefits of increased breathability do come at the sacrifice of a bit of warmth — so don't expect this layer to be quite as warm as other 250 g/m² options included in this review. Though soft, the Merino wool is slightly itchy at first and takes some breaking in (read: responsible washing and drying) before it is snuggly-comfy. We hope that designers opt to move the seams off the shoulder top with future updates, which can rub when wearing a heavy pack. Beyond these small critiques, the Meriwool Midweight Thermal presents a reasonable entry-point into all-natural base layers. It is the perfect companion for cool-weather camping during the shoulder seasons, works well for both resort and backcountry skiing, and is certainly a stylish top to be worn casually.

Read review: Meriwool Midweight Thermal

Great Value for a Lightweight Top


Outdoor Research Echo L/S


70
OVERALL
SCORE
  • Warmth - 25% 5
  • Breathability - 20% 9
  • Comfort and Fit - 20% 7
  • Drying Speed - 10% 8
  • Durability - 15% 7
  • Layering Ability - 10% 7
Materials: AirVent, 100% polyester | Weight: 3.4 oz (size Medium)
Affordable
Tough and breathable
UPF protection
Athletic articulation
Tends to hold onto odors
Not very warm
No hanging tab

If you are looking for something at a more reasonable price point, but that still qualifies as a technical, lightweight base layer, the Outdoor Research Echo L/S checks both of those boxes. This incredibly breathable, super lightweight layer is designed for sweat-inducing activities through the warmest months of the year. Perfect for climbers, runners, or really anyone who spends much of their summertime out in the sun, the added UPF 15 treatment not only helps protect your skin but also increases the longevity of this already durable crew neck.

With a little extra fabric weight compared to others in its class, when properly layered, this top will continue to keep you dry and comfortable through the winter, only adding to its value and versatility. But don't get us wrong, this is not our go-to for warmth. While we wish that the ActiveFresh odor control did a better job of keeping us smelling fresh, the Echo's small pack size and quick dry time mean we're still going to bring it along on our next expedition trip, no matter the climate. If you plan to push hard uphill — whether it's running, ski touring, biking, or climbing — you will benefit from the performance of the Outdoor Research Echo L/S.

Read review: Outdoor Research Echo L/S

Best for Backcountry Skiing


Black Diamond Solution 150 Merino


71
OVERALL
SCORE
  • Warmth - 25% 7
  • Breathability - 20% 8
  • Comfort and Fit - 20% 8
  • Drying Speed - 10% 6
  • Durability - 15% 4
  • Layering Ability - 10% 9
Materials: 78% merino wool, 22% polyester | Weight: 6.5 oz (size Medium)
Amazing odor resistance
Well-balanced weight
Articulated design
Expensive
Vulnerable to abrasion
Slower to dry

The Black Diamond Solution is our recommendation for anyone who spends their winter days seeking out fresh tracks. This 150 g/m² option strikes a nice balance between mid- and lightweight, offering more versatility to wear as the seasons transition from cold mid-winter, to sunny spring riding. NuYarn is another innovative technology, that specifically layers merino wool over synthetic fibers to best replicate the natural loft and breathability that makes the all-natural fiber so special. That means that even at a lower fabric weight, you are able to benefit from additional insulation created by an increased percentage of air pockets — without losing out on any of the breathability of this blended top.

This superior performance does come at a cost. Though the Solution may be the only base layer you need to last you all winter, it does cost nearly as much as two tops otherwise would. So it is particularly unfortunate that this prized piece is also susceptible to damage by abrasion. Fortunately, it is really intended to be worn at the base of a winter kit, rather than as a standalone top for summer activities. Even though it costs significantly more than other options in this review, its value will be apparent to guides and ski bums alike — particularly because you can actually get away with wearing this layer for multiple days, as our testers proved. While it excels as a backcountry skiing base layer, this is a great choice for any cold-weather alpine endeavor.

Read review: Black Diamond Solution 150 Merino

Compare Products

select up to 5 products to compare
Score Product Price Our Take
78
$100
Editors' Choice Award
This top is the gold standard for staying warm, dry, and comfortable during and after all of our outdoor adventures
75
$59
Editors' Choice Award
Ounce-for-ounce, this is the strongest base layer available on the market today
73
$60
Best Buy Award
A fine Merino base layer at an entry-level pricepoint
72
$129
Implementing new and innovative technology, Patagonia brings us a seamless base layer that feels unbelievable
71
$109
A technical base layer top for the 4-season, multi-sport athlete
71
$120
Top Pick Award
A high-performance value, with a revolutionary design that will appeal to anyone who spends most of their time in the backcountry
70
$49
Best Buy Award
Lightweight, versatile, and affordable, this 3-season powerhouse is ready for warmer-weather adventures
70
$55
Ready for all-day activity, but be prepared with a well-layered system if you're taking this out in the cold
68
$90
Thoughtful features like thumb loops and an extra long cut will surely help add a little extra warmth to your winter
68
$69
While it is a high-value performance layer, this silk-like Merino blend is easily damaged
66
$95
This doesn’t stand out among the crowd, but silently gets the work done without a need for recognition
64
$120
Intricate design and body-mapping technology, but falls somewhat short of hitting the mark in terms of fit
63
$80
A loose fitting, comfortable merino wool top for trail and for town
60
$40
A valuable base layer with some unfortunate flaws that undermine performance
59
$50
Ounce-for-ounce, this ultra-thin base layer is by far the warmest of our lightweight selections
55
$40
Excelling in breathability, this lightweight synthetic model is made for working up a sweat in the cold

From the highest mountains, to the deepest canyons, a versatile base...
From the highest mountains, to the deepest canyons, a versatile base layer is key to keeping you dry, comfortable, and on-the-move across the seasons.
Photo: Aaron Rice

Why You Should Trust Us


Our expert for all things comfortable and cozy is Aaron Rice. Growing up on the Atlantic coastline and living up and down the Rocky Mountains for the past decade, he knows all about making the most out of cold-weather playtime. A passion for winter weather led him to a bachelor's degree in snow and climate science — as a ski patroller and avalanche educator, you can often find him huddled in a snow pit, happily freezing his butt off to discuss the finer details of stellar dendrites. Outdoor educator and guide Roland Mott also adds experience and expertise to this review. Roland holds a degree in Outdoor Recreation Leadership and has guided rivers, backpacking, and climbing for 12 years throughout the US and Central America. He has also taught land stewardship and environmental ethics as a Master Educator for the Leave No Trace Center for Outdoor Ethics.

Click to enlarge
Click to enlarge
Click to enlarge

We identified six key metrics as essential to effectively grade a base layer top: Warmth, Breathability, Comfort/Fit, Drying Speed, Durability, and Layering Ability. Then we developed appropriate tests to carry out in the field and lab to test each metric individually. For metrics such as warmth, testing was as straightforward as wearing the garments in cold weather often and noting the relative differences. Other metrics, like durability, called for a combination of field use (i.e., chimney climbing and bushwhacking) and lab testing (repeated dry and wash cycles and an abrasion test.) From the high desert of the US Southwest to the craggy peaks of the Pacific Northwest, we wore these tops through a variety of activities—mountain biking, climbing, uphill and downhill skiing, trail running, backpacking, and more—testing and assessing their relative strengths and weaknesses along the way.

Related: How We Tested Base Layers

Analysis and Test Results


As a workhorse for thermoregulation, we understand the importance of having a base layer that will serve you well through all of your outdoor pursuits. That's why we started with only the best tops on the market and then proceeded to field test the heck out of them. By submitting them to the wear-and-tear of everyday use and a variety of outdoor activities across a spectrum of temperatures and environments, we are best able to dial in which types of layers work best in what situations. We targeted the most important qualities to analyze and tested these layers side-by-side according to these metrics. We offer this comprehensive review to help you land on the best base layer for your own needs.

Related: Buying Advice for Base Layers

It is important to note that the assigned scores are determined relative to the other products in the review. We purposefully chose to test the best layers on the market, so a low score in our testing does not mean a product is not worth its mettle. It simply means it performed poorly in relation to the competition. We understand that the individual metrics that are important to some may not be as important to others. By testing and rating each of these layers relative to one another, we can highlight which score highest in the metrics that are significant for how you intend to use it. Our ratings are based on specific tests we perform and backed up by personal experience while using each of these products extensively in the field.


Value


The balance between price and value is a fine line to walk when researching a product. The argument of synthetic vs. all-natural fibers is a perpetual battle in the recreational apparel world, and we like to think of ourselves as conscientious objectors in this fight. But for the sake of producing quality reviews, alas, we must decide from time to time what materials are the best for certain situations. There are certainly pros and cons to each material type.

Early bird gets the worm, or a summit bid all to ourselves in this...
Early bird gets the worm, or a summit bid all to ourselves in this case. The boys all wore different weights of merino wool baselayers on this climb up Mt. Hood.
Photo: Adam Zagorski

Synthetic fabrics tend to be less expensive, a touch more durable, and pack down smaller. They also tend to hold onto moisture, retain odors over time, and often don't provide the same warmth-to-weight when compared to their natural-fiber companions. Merino wool tops are typically more expensive and bulkier but offer benefits like superior body-temperature regulation, moisture-wicking ability, and odor resistance. Silk, while incredibly valuable in terms of warmth-to-weight-to-thickness, is a hard sell based on durability alone.

Less, sometimes, is more -- if you're looking to go fast-and-light...
Less, sometimes, is more -- if you're looking to go fast-and-light on your next backpack, think about investing in good base layers that can be worn in a wide-range of temperatures, and allow you to ditch some of your bulkier clothing when the season permits.
Photo: Jill Rice

The Outdoor Research Echo L/S is one of the most valuable synthetic layers on the market today. A standout for 3-season recreation and as an athletic base for the coldest months, this top is not only versatile for activities like backpacking, but performs impressively well as a technical layer. If you're value-minded but tend to run colder, add a little warmth with an all-natural option like the Meriwool Thermal Midweight, a 100% merino wool layer that is very reasonably priced compared to its direct competition.

A high quality merino wool base layer, like the Meriwool Midweight...
A high quality merino wool base layer, like the Meriwool Midweight Thermal, is an investment in your comfort. (It's even reasonably priced enough to appeal to truck-dwelling climber types.)
Photo: Jill Rice

Purposeful Purchasing


One of the best ways we believe to determine value is to start with the question: How do I intend to use this particular layer? Do I want something that will keep me warm during the darkest months of winter? Or do I want something to run in when temperatures start to taper off in the fall? These types of questions will help guide you in the direction of what holds more importance for you as a buyer, ultimately helping you be a better-informed consumer. Decide which metrics are most important for your sport or activity — whether it's ice-climbing or shoveling snow in your driveway — and base your decisions on those factors first.

Warmth


As the foundation of your layering system, warmth is one of the most important qualities to consider in your decision. It is not just about simple heat retention, but rather the complex system of thermoregulation. A good base layer should trap heat to keep you warm in cold temperatures and also allow excess heat to escape when your heart rate climbs and body temperatures rise. It also involves wicking away sweat to keep you dry and protected from evaporative cooling. All of these ingredients are essential to a layer's ability to keep you warm and dry through a range of temperatures. An intensely warm top that doesn't breathe well may work for ice fishing, but it will likely leave you dangerously wet and cold during high-output activities like backcountry skiing.


We wore these layers through the varying temperatures of fall and winter to test every quality that results in you successfully staying warm and dry. We wore them as we skinned up windblown ridges in the Northwest, rowed through desolate canyons in the Southwest, slept on the frozen dirt after climbing sunny sandstone cracks, and explored trails by bike and foot in Colorado and New Mexico. The standout tops for well-balanced warmth are the SmartWool Merino 250, the Patagonia Capilene Air, and Ridge Merino Inversion. These tops consist of thicker, cushy fabrics that seal in heat while maintaining excellent breathability and moisture-wicking abilities.

Ski patrollers are up and working hard well-before first chair...
Ski patrollers are up and working hard well-before first chair (perks of the job.) The job demands a base layer that is able to insulate against frigid, pre-dawn temperatures, and thermoregulate to keep you dry enough to work all day... the perfect job for the SmartWool Merino 250.
Photo: Aaron Rice

For those who work in extremely cold conditions or normally run on the chilly side, you may want to seek out those tops that favor pure warmth over breathability. The REI Silk Crew is an impressively warm, surprisingly thin layer that can supplement winter-wear without adding much bulk. For the deep cold of winter, we recommend the Smartwool Merino 250 or the Ridge Merino Inversion, the heaviest 100% merino layer top we tested. This top is designed specifically with snow sports in mind, incorporating features like thumb-loops and an extra-long hem, both of which help minimize skin exposure to cold air. And as an intriguing option to split the difference between light- and mid-weight, the Black Diamond Solution is as equally suited to working hard in the skin track as it is working all day in the snow. The Norrona Wool Round Neck is similarly weighted to the Solution and is very similar in terms of offering a nice middle ground to split the seasons.

While not always the case for synthetic tops, we find that with base...
While not always the case for synthetic tops, we find that with base layers knit with either full merino wool or a merino-blend, the heavier the garment, the warmer it tends to be. The Ridge Merino Inversion is one of the heaviest, and one of the warmest layers in this review.
Photo: Jill Rice

If you are looking for a layer that better suits highly aerobic activities or you want versatility across seasons, you will likely benefit from choosing a lighter weight layer that prioritizes breathability over warmth. One of testers' favorite for an aerobic layer is the Patagonia Capilene Cool Lightweight — this top is perfect for 3-season activities like backpacking or mountain biking. For cross-country and backcountry skiing, we would opt for lightweight layers that still offer a bit of warmth, like the NW Alpine Spectra, Outdoor Research Echo L/S, or Patagonia Capilene Cool Merino. If you're a rock-climber anticipating long-belay stances and short bursts of energy, check out the Patagonia Air Crew, Icebreaker 200, or SmartWool Merino 250, which all provide a solid level of warmth but still offer impressive breathability.

Casual alpine cows. The Patagonia Capilene Cool Lightweight...
Casual alpine cows. The Patagonia Capilene Cool Lightweight long-sleeve is a great option for warm-weather backpacking.
Photo: Jill Rice

There are some specific features that we've found to help keep us warm and may help you narrow your search for the perfect base layer. Models like the Icebreaker 200 Oasis, Smartwool Intraknit 200, and both the REI Co-op Merino Midweight and the REI Lightweight Crew have nice long arms and a drop-tail hem. Like the extended-cut of the Ridge Merino Inversion, this design feature helps them to stay tucked into your bottoms when skiing. They also keep them from rising up and exposing your wrists, back, and belly when bending over to put on your climbing skins or reaching for that next crimper when climbing.

Making our way down from the summit of Mt. Hood during a winter...
Making our way down from the summit of Mt. Hood during a winter ascent. This climb is a true test of a base layer. Skinning and sweating in pre-dawn subfreezing temps for hours, then standing still on the windy summit, and finally 6,000 feet of downhill skiing. The Smartwool 250 rules in these environments.
Photo: Roland Mott

The Argument Against Cotton


There are significant differences between a natural fiber (Merino wool, silk) and a synthetic fabric (polyester, polypropylene) when it comes to warmth. The key here is that they both continue to insulate when wet. Comparatively, cotton can absorb up to 100% of its material weight in moisture, leaving you wet, cold, and miserable, and may be quite dangerous in certain situations in the backcountry.

Breathability


Breathability is the yin to warmth's yang. Alongside warmth, it is arguably the most important quality of an effective base layer. Breathability is tied mainly to the moisture-wicking capability of a fabric. Effectively, this is the ability to collect moisture (sweat) and move that moisture to the outside surface of the fabric, where it can freely evaporate. The breathability of a garment is determined by how quickly and efficiently a fabric can convert sweat to free water vapor. A quality, breathable layer will help regulate your body temperature through a range of environments, regardless of your energy output. Depending on the situation, a great base layer will effectively work to keep you dry and warm, or dry and cool, depending on how it's designed.


Breathability is an extremely important quality during active pursuits, as well as stop/start activities like backcountry skiing or rock climbing. A breathable shirt will allow the moist air hovering over your skin to escape through the material without saturating the fabric, thus keeping you warm and dry. A non-breathable shirt will prevent that moisture from escaping, leading it to condense on the inside of the garment. This leaves you wearing a sweat-saturated shirt that is wet, heavy, and potentially dangerous in cold conditions.

The Outdoor Research Echo L/S is the perfect top for long trail...
The Outdoor Research Echo L/S is the perfect top for long trail runs, or any heart-pumping activity through the warmer parts of shoulder seasons, or just chilly summer mornings.
Photo: Jill Rice

We assessed each layer's breathability systematically to back up our findings after months of use hiking, running, skiing, climbing, and biking. We tested each layer side-by-side in a temperature-controlled, indoor environment. We used the same short, rigorous exercise routine to work up a sweat, and then after stopping, timed how long it took for our skin and the inside of our shirts to dry.

The Patagonia Capilene Air proving its versatility, keeping us cool...
The Patagonia Capilene Air proving its versatility, keeping us cool and comfortable in the fall Utah Sun. Its nearly see-through fabric allows for air to pass through it with ease making it extremely versatile for conditions ranging from super cold when layered, to warm weather as a stand-alone layer.
Photo: Roland Mott

Not surprisingly, the tops that earn our highest scores for breathability are also the lightest weight fabrics that incidentally didn't score as well in the warmth metric. Those are the Patagonia Capilene Cool Lightweight and Capilene Cool Merino, the NW Alpine Spectra, Helly Hansen Lifa Stripe, and Outdoor Research Echo L/S. As a bit of an outlier, the Patagonia Capilene Air continues to impress with its unique ability to balance warmth and breathability masterfully. We appreciate merino-blended options like the Norrona Wool Round Neck and Black Diamond Solution as slightly more insulated options, that still prove themselves remarkably well during the warmer seasons. You may notice that these two layers tip the scales at relatively the same material weight — for wool tops, there is a clear connection between weight and breathability.

Enduro-style mountain biking is a great way to to test the...
Enduro-style mountain biking is a great way to to test the breathability of these layers, with grueling uphill pedals followed by equally demanding downhill drives. Though the Patagonia Capilene Cool Merino excels in this capacity, a lack of durability wouldn't make this our go-to bike jersey.
Photo: Jill Rice

Comfort and Fit


When choosing between options, comfort and fit are usually at the top of the list for many consumers. Even if it excels in all other categories but fits you poorly or is uncomfortable, it won't serve you in your quest to send. This may be the toughest metric to rate because comfort and fit are ultimately subjective and different for everyone's preferences and body types. We try our best to give as subjective of an opinion as possible when considering all the factors that play into a layer's comfort and fit. We scrutinized each layer and asked the following questions: How does the fabric feel next to your skin? Is it soft, itchy, stretchy, static, warm, or cool? Does it glide against your skin or cling too tightly?

The SmartWool Intraknit is impressively warm for its weight. What...
The SmartWool Intraknit is impressively warm for its weight. What you can't see is that our buddy is climbing in a puffy, while we had no problem hanging out for long-belays in the shade.
Photo: Jill Rice

Secondly, we considered how the garment generally fits: Is it too loose, too tight, does it constrict in particular areas — like the shoulders? How are the lengths of the torso and sleeves - does it expose your belly and wrists when reaching up? How are the cuffs? Are they too tight? Do they stretch out and lose shape when worn pulled up on your forearm? Is the neck comfortable? Is it loose, letting cold air draft in like a barn door, or is it too tight? What about mobility? Does the fabric have stretch? Are there gusseted underarms, purposeful stitching patterns, or articulated zones to help freedom of movement?


Armed with this long but scrutinizing list of questions to critique each layer, we learned a lot about how a layer will perform. We're only human; we gravitated toward tops that were soft and comfortable next to skin. The comfiest layers are the Patagonia Capilene Air, SmartWool Merino 250, REI Co-op Merino Midweight, Ridge Merino Inversion, and the Patagonia Capilene Cool Merino. A surprising turn-out concerning comfort is the NW Alpine Spectra, a full-synthetic blend that magically feels like merino wool, thanks to the extra-pliable Spectra fibers.

Alpine adventures require that your clothing doesn't hold you back...
Alpine adventures require that your clothing doesn't hold you back when the situation means you have to make that move. The stretch and articulated design of the Black Diamond Solution makes it an ideal alpine first layer.
Photo: Aaron Rice

We prefer tops with sleeves that don't tend to creep up our arms, and a longer torso that avoids the always undesirable belly exposure. Slim-fitting sleeves and waists, combined with well-stitched hems and cuffs tended to do the best. The tops that really do a great job of balancing fit and comfort are the SmartWool Merino 250, Patagonia Capilene Air, Icebreaker 200 Oasis, and the Patagonia Capilene Cool Lightweight. The Ridge Merino Inversion and Black Diamond Solution also fit this mold and are the only layers that incorporate thumb loops. Performing the most poorly in this category was the Helly Hansen Lifa Stripe with an extremely short torso, resulting in belly exposure at an all-time high. Not far in front of that was the Smartwool Intraknit 200, whose tight-fitting arms and shoulders were in no way benefited by the stretch and engineered articulation of the material. The REI Silk Crew, unfortunately, does not have the benefit of style or a graceful design.

A 360-degree view of the handsome fit of the Meriwool Midweight...
A 360-degree view of the handsome fit of the Meriwool Midweight Thermal. Our head tester is 5'10", 155lbs, wearing a size medium.
Photo: Jill Rice

Quality of construction and thoughtful seam patterns were nice touches that increase comfort as well as mobility. We appreciated the fit of the Icebreaker 200 Oasis, the Patagonia Capilene Cool Lightweight, and the NW Alpine Spectra. The well-articulated seam patterns of the Outdoor Research Echo L/S, Norrona Round Neck, and Black Diamond Solution pull seams down from the shoulders where they often rub under the weight of a backpack and add an extra side panel for increased upper-body mobility.

As we describe before, a thoughtfully articulated design increases...
As we describe before, a thoughtfully articulated design increases mobility in the Black Diamond Solution. This top has a raglan-style cut, with flatlock seams that isolate the shoulders and back from the torso.
Photo: Jill Rice

A few tops were able to stand out for their superb comfort and fit while a couple left much to be desired. The Champions of Comfort are easily the SmartWool Merino 250, Patagonia Capilene Air, and Ridge Merino Inversion, all boasting soft, plush, cushy fabrics. Though on the thinner side, the Patagonia Capilene Cool Merino sports a magical, almost silk-like merino wool blend. Struggling in this category is the Helly Hansen Lifa Stripe, with a tight neck that chokes us out, super short torso, and thick sleeve cuffs. Similarly, the Smartwool Intraknit 200 didn't fare well here with unusually long arms, uncomfortably narrow shoulders, and tight-fitting biceps.

Shop Local


If possible, we always suggest trying garments on in person as it is the only way to know whether it will fit you well, and saves you the time, hassle, and carbon impact of shipping and returning.

Underarm gussets, combined with the partial spandex construction...
Underarm gussets, combined with the partial spandex construction, certainly improve the reach and general movement of the REI Lightweight Crew.
Photo: Jill Rice

Durability


Durability is a characteristic that we search for in all of our outdoor gear. We often spend on high-quality products to own fewer things that will last us longer and thus stay out of the landfill. Base layers should adhere to the same purchasing ethics that we apply (or should) to all of our consuming habits. Buy less. Buy quality. Repair when possible. When that's not possible, opt for post-consumer products — many of the polyester layers included in this review are at least some part recycled polyester.


To test durability, we inspected the strength of the fabrics and the quality of the stitching and construction of the pieces as a whole. We also dragged them up against rocks, rolled in the dirt, plowed through manzanita and chaparral bushwacking to get to beautiful places, and subjected them to merciless amounts of washing and drying cycles. To test abrasion resistance in a controlled environment, we ground the elbows of the fabric a set number of times across a one-foot distance of gritty granite to see how the fabrics faired (think wash-board technique). This specific test gave us a very clear idea of how certain tops held up to abrasion. The Patagonia Capilene Cool Merino is the least durable top overall that we tested — think fine silk — but performs exceptionally in all other categories.

Making its way up an Eldo classic, the SmartWool Merino 250 shows...
Making its way up an Eldo classic, the SmartWool Merino 250 shows off its ability to breathe and keep you comfortable in warm conditions as well as cold. The thick merino fabric makes it the most durable merino layer that we tested.
Photo: Roland Mott

The broad consensus is that merino wool is, generally speaking, less durable than synthetic fabrics. Yet in our abrasion test, the thick fabric of the SmartWool Merino 250 Crew showed only surface wear. The thickness of the wool is directly correlated to its durability level, but factors such as quality of materials and construction can also affect the durability of a garment. Other factors that contribute to staying-power are flatlock seams, which you will find featured on the majority of the layers in this review.

Synthetic material has the tendency to drop seams after repetitive...
Synthetic material has the tendency to drop seams after repetitive use, but with no actual damage to the face fabric; flat-lock seams hold the tough Outdoor Research Echo L/S together.
Photo: Jill Rice

Merino wool and silk, historically, are notorious for their lack of durability, wearing holes through the fabric or shrinking/losing its shape through washes. Merino wool has come a long way in the durability that it offers — particularly considering merino wool/polyester blends. But when it comes to longevity, natural material still falls behind its synthetic counterparts. For a lot of folks, the performance benefits of merino wool outweigh the lack of durability, and if you take proper care of your merino top, it can serve you for a long time. Despite its reputation as being a relatively short-term fabric, several of our testers have gotten many years of use out of their merino wool tops. That said, they try to be careful to hang dry them and not wear them every single day (they are comfortable enough to want to in the winter).

Durability is paramount for base layers that are going to pull...
Durability is paramount for base layers that are going to pull double-duty as standalone shirts for rugged activities like mountain biking. Regardless of weight class, the NW Alpine Spectra is hands-down the most durable layer we tested.
Photo: Jill Rice

The shortest path to the grave for both merino wool and silk is through consistent washing, and particularly tumble drying, of the garment. In fact, most manufacturers indicate that their wool layers are not dryer safe, and instead suggest lying the garments flat to dry. Merino wool fibers are naturally antibacterial, paired with their incredible ability to wick sweat and dry quickly. This fabric holds an uncanny power to resist body odor, whereas synthetic fabrics are infamous for quickly holding onto and even enhancing stink. This means that wool can be worn more and washed less, increasing its longevity. We suggest limiting washing merino layers when they are visibly dirty, or you manage to wear them enough for them to stink eventually.

The REI Silk Crew is one of the very few tops that wore completely...
The REI Silk Crew is one of the very few tops that wore completely through during our laboratory abrasion test.
Photo: Aaron Rice

If you'll be wearing this top to scrape through slot canyons and drag yourself up rock chimneys, then durability is probably a quality you're going to want to think about. As the only company in the world currently using this innovative fiber in clothing, the NW Alpine Spectra stands far above all others in this review in terms of durability. In our abrasion tests, we could barely get this top to show signs of wear. Throughout testing, its performance seemed to back the strong claims made about this fabric fiber technology.

Merino Care


Although some Merino wool garments give the OK to tumble dry on low, we suggest washing on a cold cycle and laying to flat dry. This will increase the longevity and fit of your shirt.

Drying Speed


Staying dry is a foundation of being comfortable in the outdoors. Whether you need to cool down or stay warm, being wet can severely inhibit your ability to access happiness and joy. Sometimes the moisture comes from outside sources like rain or snow. Other times, it comes from a deep well of desire to work hard and push yourself, rising up to the surface as sweat. No matter where it comes from — physically or metaphorically — a top's ability to dry quickly on the body is important.


It's worth addressing that the drying speed of a fabric can differ depending on whether it is being worn or left out to dry — flat dry times and dry times on the body sometimes vary. We do expect, and often experienced, a strong correlation between drying speeds when laid flat and when worn — that is, tops that dry faster on the clothesline also tend to dry faster on our bodies. The Outdoor Research Echo L/S was a perfect example of this, flat drying in as little as a half-hour, and simultaneously preventing moisture build-up on our skin, regardless of climate or body temperature level. But, of course, there are exceptions to this rule. The REI Silk Crew, with its ultra-lightweight design, had the fastest flat drying time. However, when it comes to breathability and drying out during activity, silk falls far behind rival synthetic materials.

When the going gets tough, its important to have a base layer, like...
When the going gets tough, its important to have a base layer, like the Patagonia Capilene Cool Lightweight, that will actively dry out on your body.
Photo: Jill Rice

Our drying speed test was a simple one. We fully saturated all of the products and then laid them out to dry at the same time, then recorded the times it took for each layer to surface dry, as well as the time it took for them to dry completely. Merino wool claims that it can absorb up to 30% of its weight in moisture before feeling wet to the touch. This seemed to prove true as we had to agitate and compress the wool layers while submerged for the fibers to become saturated — a plus if you are planning to wear these layers stand-alone in wetter, more mild climates. The Merino wool/polyester blends of the Patagonia Capilene Air and Smartwool Intraknit 200 did a great job at resisting absorption.

Colorful and practical, our soak n' dry test seeks to replicate how...
Colorful and practical, our soak n' dry test seeks to replicate how you would hand wash and air dry shirts while on an expedition or extended backcountry trip.
Photo: Aaron Rice

An obvious observation was that thinner fabrics dried significantly faster than thicker ones, to no one's surprise. As mentioned above, the REI Silk Crew dried lightning-fast, closely followed by the Patagonia Capilene Cool Merino and Capilene Cool Lightweight. Coming in close behind with admirable dry times for synthetic layers were the Helly Hansen Lifa Stripe and NW Alpine Spectra. Notably, the merino wool Icebreaker 200 Oasis dried quicker than the other wool layers of similar weight. The Ridge Merino Inversion, with the thickest fabric weight of any merino layer we tested, came in last in this category.

Consider when and how you plan to use your base layer. Choosing a...
Consider when and how you plan to use your base layer. Choosing a layer that balances active drying and warmth is crucial for sports like backcountry skiing.
Photo: Aaron Rice

Layering Ability


The ability to layer well is an often overlooked consideration but is important for practical use in the outdoors. One of the greatest qualities of a base layer is its versatility to be worn as a single layer when you need just a little something or to be layered in a myriad of ways to keep you warm and comfortable in any temperature or situation.


To test layering ability, we thought of every way a top could be layered, and we tried all the combinations out on every garment. We observed how easy they layered as well as how they fit and felt: next to skin, over a t-shirt, over another base layer, under a sticky and tight fleece mid-layer, a sweatshirt, a puffy, a rain shell, as well as stacked in a full layering system of first (base) layer, mid-layer, puffy, and hard shell. While all layers performed well next to skin, a few did great in other areas also.

An example of a layering system. Base layer, fleece mid layer, soft...
An example of a layering system. Base layer, fleece mid layer, soft shell, and down puffy. The Patagonia Capilene Air, pictured here, traps heat extremely well in a layering system but as a stand-alone layer, air cuts right thru it.
Photo: Roland Mott

The most form-fitting layer next-to-skin is the Icebreaker 200 Oasis, and not far behind that are the Norrona Wool Round Neck and Black Diamond Solution. While the REI Silk Crew is awkwardly baggy, its sheer construction allows it to layer underneath practically anything easily, including heavier-weight options. Looser, more relaxed fitting tops that layered well over another lightweight shirt are the Smartwool Merino 250 and the REI Merino Midweight.

Thinner base layers, like the Patagonia Capilene Cool Lightweight...
Thinner base layers, like the Patagonia Capilene Cool Lightweight, are designed to keep you dry and comfortable at skin level. Mid-layers are intended to add insulation, and a shell helps to keep you protected from the elements.
Photo: Jill Rice

Conclusion


With such a wide array of options out there, it can be tough to narrow your search down to the layer that best suits your body type, internal temperature inclination, and intended uses. We conducted all our tests and collected our experiences into this review to try and help you choose the layer that will become your adventure sidekick for years to come. It's important for you to consider the activities, temperature ranges, features, and qualities when choosing a new base layer top. We wish you luck in your honorable outdoor pursuits of fun.

Aaron Rice and Roland Mott