The Best Long Underwear and Base Layers for Women

What's the best women's long undershirt shirt? We picked through 60 different products and purchased nine of the industry's best to test side-by-side. We wore each as a stand-alone top while climbing, hiking, and backcountry skiing. We also layered them underneath sticky mid layers to truly test their potential as a base layer. During our testing period, each flew with us down snowy mountains or while conquering trails. Each saw its fair share of precipitation while being subjected to objective tests performed in our lab. In the end, we evaluated each base layer a choose a few select award winners. We learned that while all shirts performed well through our tests, some just stood out above the rest.

Read the full review below >

Test Results and Ratings

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Analysis and Award Winners


Review by:
Amber King
Senior Review Editor
OutdoorGearLab

Last Updated:
Tuesday
March 27, 2018

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Updated March 2018
Preparing for upcoming adventures this year? A baselayer is a key piece to any adventurers outdoor wardrobe. This year we've added a couple more contenders and updated current reviews to outline key changes since our last review. There are new and exciting award winners in addition to Top Picks that might be exactly what you've been looking for.

Best Overall Women's Long Underwear


Smartwool Merino 250 1/4 Zip - Women's


Editors' Choice Award

$70.00
at Amazon
See It

Materials 100% Merino Wool | Style: Zip-neck
Super cozy fabrics
A wide range of thermoregulation
Quick-to-wick
Versatile fit
Cute
Heavy when wet
Not super durable
Wear this super comfy midweight base layer from the trail to your bed! The Smartwool Merino 250 ¼ Zip wins our Editors' Choice award for its fantastic comfort and versatility. Loaded with 100% natural Merino wool fibers, this top provides one of the widest ranges of thermoregulation tested. It functions well as a base layer and a wear-alone top in temperatures ranging from the double negative digits to highs of 70 degrees Fahrenheit.

It outperformed every other shirt in this review because of its ability to keep us dry and comfortable when conditions went from warm to cold and wet to dry. The fabric wicks away moisture, dries quickly when on, and doesn't stink. We only wished it was a little more durable! As a result, this is the favorite amongst our testers and our Editors' Choice award winner!

Read review: Smartwool Merino 250 1/4 Zip - Women's

Best Bang for the Buck


REI Co-op Midweight Base Layer Crew - Women's


Best Buy Award

$49.95
at REI
See It

Materials: 92% Polyester, 8% Elastane | Style: Crew
Soft materials
Great price
Easy to layer
Stretchy and versatile fit
Lightweight
Fast to dry
Smelly over time
Doesn't wick as well as Merino wool
Not super warm as a base layer
Keeping tabs on your wallet? The REI Co-op Midweight Crew may be a perfect fit! This 100% polyester midweight long underwear top costs only $50 retail, with deals for even less online! Our testers appreciated it's smoother face-fabrics that made layering easy in addition to its stretchy fit.

As one of the fastest drying tops tested, its a perfect option for those who might encounter sweaty situations or precipitation. The fabrics are also soft to the touch, don't itch, and feel nice on the skin. While it's not the warmest base layer out there, we still appreciate its ability to keep us warm in cool weather. Take home this synthetic Best Buy award winner.

Read review: REI Co-op Midweight Base Layer Crew Women's

Top Pick for Versatility


Arc'teryx Rho LT Zip - Women's


Top Pick Award

$125.00
at MooseJaw
See It

Materials: Torrent (84% polyester, 16% elastane) | Style: Fitted zip-neck
Cozy and warm
Fitted design that's easy to layer
Longer fit through arms and torso
Stash pocket
Ultra-durable and well-crafted
Lacks impeccable breathability
Expensive
Smelly over time
Seeking a technical base layer? The ultra-versatile Arc'teryx Rho LT Zip wins our Top Pick! This 100% polyester baselayer is super durable and holds up in the crud. Our main tester has owned this shirt for over five years and chose to wear it for a plethora of activities ranging from backcountry split-boarding in Alaska to rafting the Grand Canyon. Through these experiences, we learned that this layer is warm, well-fitted, and thermo-regulates well for its weight.

While it's not as breathable as other layers in this review, it still does a decent job wicking away sweat to keep us dry. We also love the extra stash pocket on the left arm that is just the right size for a credit card or key. The interior is soft and warm, making it a perfect piece to wear against the skin. We also appreciate the zip-neck, which makes it easy to vent when temperatures start to creep a little higher. Overall, this ultra-durable layer is one of our favorites and functions well for pretty much anything!

Read review: Arc'teryx Rho LT Zip - Women's

Top Pick for Everyday Wear


Smartwool Merino 250 Base Layer Crew - Women's


Top Pick Award

$94.95
at MooseJaw
See It

Materials: 100% Merino Wool | Style: Crew and patterned (others available)
Super comfortable merino wool
Fantastic temperature regulation
Stylish patterns
Natural fibers resist odors
Expensive
Not durable
Not quick to dry
The Smartwool Merino 250 Crew - Women's wins our Top Pick for Everyday Wear for its incredibly comfortable fabrics and cute patterns. Built out of 100% merino wool, this top feels amazing on the skin. The fabric falls comfortably around curves and stretches where it needs too. The cute patterns offered makes it perfect for not only outdoor adventures, but wearing to work or out with a group of friends.

The fabric keeps the skin dry and comfortable even when the temperatures dip or the sky pukes rain and snow. If you're looking for a shirt that can be worn out on the trails just as much as around town, this Merino wool beaut may be exactly what you've been searching for!

Read review: Smartwool Merino 250 Base Layer Crew - Women's

Top pick for Breathability


Patagonia Capilene Midweight Crew - Women's


Top Pick Award

$43.99
at MooseJaw
See It

Materials: 100% Polyester| Style: Crew (Other styles and weights available)
Great temperatures regulator
Versatile
Inexpensive
Quick to dry
Boxy, not fitted
Scratchier fabrics
Pills after a few washes
Tried, tested, and true, the Patagonia Capilene Midweight Crew - Women's is a classic workhorse shirt that will keep you happy for years to come. Featuring a 100% polyester design with a Polartec Power Grid design that allows ample air-flow, this is our Top Pick for breathability! The face fabric provides a touch of wind-resistance not found in any other base layer.

It's easy to layer shirts over or under, making it a great choice for sweaty sports like trail running or cross-country skiing. Feel free to sport on warmer days or as a base layer during colder months of the year. This quick-to-dry Top Pick will keep you comfortable in cool to warm temperatures throughout the year.

Read review: Patagonia Capilene Midweight Crew - Women's

select up to 5 products
Score Product Price Our Take
81
$100
Editors' Choice Award
This 100% Merino Wool is our Editors' Choice for its cozy fabrics and amazing performance in all conditions.
78
$125
Top Pick Award
This Top Pick is our favorite synthetic base layer that excels in warm to cold weather.
76
$50
Best Buy Award
A fantastically versatile baselayer that wins our Best Buy Award this year!
75
$79
If you seek a high value Merino wool mid-weight base layer, this is our top recommendation!
75
$105
Top Pick Award
Add this Top Pick to your wardrobe as a stylish and functional mid weight base layer for all four seasons.
74
$110
Enjoy the warmth and wide range of thermoregulation offered by this 100% merino wool contender.
70
$59
Top Pick Award
With the fastest drying speed and great durability, this Top Pick will keep you dry during your next outdoor adventure.
68
$50
This midweight synthetic base layer is quick to dry and absorbs very little water.
65
$110
This is the most durable 100% Merino wool base layer tested.

Analysis and Test Results


For an avid outdoor adventurer, a base layer or piece of long underwear is of utmost importance for a functional layering system. It's responsible for wicking away moisture generated from activity to ultimately keep you warm. During our testing period, we called upon many women to test each long underwear shirt in a gauntlet of conditions. We took each backcountry skiing in the Rocky Mountains, rode lifts at resorts in Washington, and conquered trails all around the world. We tested each top as apart of a layered system and on its own.

A look at all the different women's base layers tested in this review.  Top (L to R): WoolX Hannah  ATX Rho LT  North Face Warm Crew Middle (L to R): Patagonia Midweight Capilene  Smartwool 250 1/4 Zip  Smartwool 250 Crew Botton (L to R): REI Midweight Crew  Icebreaker Tech 260 Crew  Kari Traa Zip
A look at all the different women's base layers tested in this review. Top (L to R): WoolX Hannah, ATX Rho LT, North Face Warm Crew Middle (L to R): Patagonia Midweight Capilene, Smartwool 250 1/4 Zip, Smartwool 250 Crew Botton (L to R): REI Midweight Crew, Icebreaker Tech 260 Crew, Kari Traa Zip

To determine our testing criteria we talked to numerous female mountain guides, runners, and outdoor enthusiasts about the most important considerations for a base layer. Our top responses are reflected in our metrics: Warmth, Breathability, Comfort & Fit, Layering Ability, Drying Speed, and Durability. While this article provides an overview of the best contenders for each metric, you can simply click on the link for any base layer to learn more about how it specifically did in each metric. We hope this in-depth analysis will help you find the right long underwear top for you throughout all four seasons!

The synthetic Rho LT Zip wins our Top Pick for versatility for its great performance in an array of conditions.
The synthetic Rho LT Zip wins our Top Pick for versatility for its great performance in an array of conditions.

Warmth


When choosing a long underwear top, warmth is one of the most important factors to consider. A base layer that keeps you warm, especially in cool to cold weather, will allow you to adventure without having to stop and warm yourself. When considering the warmth of a long underwear shirt, there are two main factors to consider. First; the weight of the layer. A heavier weight typically equals more warmth. Lightweight equals less warmth and most commonly better breathability.

The fabrics wicking abilities in a layered system is another important aspect to consider. It is essential that the fabric can wick sweat away from your skin. If the material is unable to do this, sweat will eventually cool down, which inevitably leads to a drop in your core temperature. If you seek a warm base layer, be sure to make sure your shirt will perform. To test this, we exposed ourselves to cold temperatures during the winter Polar Vortex of 2017-18 in Northern Canada. We wore each layer as apart of a layered system and on its own.


Merino Wool
After hiking, skiing, and climbing with each base layer, we have noted that Merino wool is warmer than tops of synthetic construction. The Icebreaker Tech 260 Midweight is the warmest base layer tested with 260g of 100% Merino wool fibers. The shirt is heavier in weight and kept us warm as a base layer while the Arctic winds blasted us during the Polar Vortex on the East Coast this last year. It, like the Smartwool Merino 250 ¼ zip, our Editors' Choice winner, kept us warm in a layered system when temperatures got well into the double negatives.

Freezing our buns off on a negative 20-degree day  we test the capabilities of the super warm Icebreaker 260 in a layered system while running five miles through the pavement jungles of Mississauga  Ontario. Despite the frozen eye-lashes  we were still smiling!
Freezing our buns off on a negative 20-degree day, we test the capabilities of the super warm Icebreaker 260 in a layered system while running five miles through the pavement jungles of Mississauga, Ontario. Despite the frozen eye-lashes, we were still smiling!

That said, the Smartwool Merino 250 ¼ Zip wasn't as warm on its own because of its thinner construction and loosely woven face fabric that lost heat more quickly. We did, however, like the functioning zip-neck that locks in warmth around the collar on super windy days. Another Merino wool contender that scored high in warmth is the WoolX Hannah, earning an eight out of ten (similar to the Smartwool options) for its longer fit, providing ample coverage. With just 230g of Merino wool, it is not as stacked as the Smartwool tops, but the face fabric is more tightly knit, locking in warmth better. All shirts did an excellent job at wicking away moisture for quick evaporation, except for the 240g Kari Traa Rose H/Z because of it's super tight-knit construction. While this provided ample warmth while sitting still, it had us shivering after sweating when we took a little break.

Synthetic Options
Polyester simply isn't as warm as Merino wool because it holds moisture in the fabric when worn. When trail running on a warm day, we went from warm to cold temperatures and noticed that polyester fabrics held more moisture, making us shiver when stopping for lunch. This is a weird observation as synthetic typically dry much faster (which we'll talk about later) when dried in the sun or a dryer. However, when worn against the skin, the material simply doesn't wick as well as Merino wool. We also think that the synthetic fibers simply don't generate as much heat.

Providing ample warmth in the high mountains of Alaska  we test the warmth of the Rho LT while splitboarding on this eight-mile tour over glaciers and corniced precipices.
Providing ample warmth in the high mountains of Alaska, we test the warmth of the Rho LT while splitboarding on this eight-mile tour over glaciers and corniced precipices.

While synthetics typically aren't as warm as Merino wool, some competitors have kept us as warm as both a base layer and as a wear-alone top. The Arc'teryx Rho LT Zip makes the top of the list with its 82% polyester (and Elastane) architecture hat hugs the body. The interior is fleece-lined which generates even more heat. It wicks well and is one of the warmest base layers because of its wind-resistant face fabric that is super tightly knit, and it's super fitted design. The REI Co-op Midweight Base Layer is our Best Buy winner that has 92% polyester (more than the Arc'teryx), but the thinner fabrics that aren't as wind-resistant, making it not as warm when worn on its own. As a base layer, it performs similarly to The North Face Warm, generating a decent amount of heat on the move. As mentioned above though, we found all these warmer synthetics are a little more prone to holding moisture (especially in a layered system) and thus, they didn't score as high. They are a great option if you need something that is durable and dries out quickly.

In this review we compared just midweight layers that are meant for warm to cool weather. If you plan on being in some of the coldest weather on Earth, a heavier weight might be necessary, whereas if you are going adventure when the sun's a-blazing, a lighter weight will do you well. All tops tested have a wide range of different weight categories. So if you want to beef up or slim down on warmth, choose the correct weight.

Breathability


Playing a key role in thermoregulation, breathability is how well the fabric allows heat to escape, providing venting capabilities in addition to less affinity for you to sweat on the trail. When worn in a layered system, breathability enables fabrics to move moisture from the skin to the exterior. If you have a less breathable mid-layer or jacket on, it could lock in unwanted moisture. So a breathable layered system is key. If you wear the shirt on its own, a breathable base layer is for aerobic activities like trail running, cross-country skiing, or riding bikes in the backcountry.


In our testing period, we wore each shirt without a layered system. Specifically, we took each trail running and hiked uphill for miles on end to see which ones allowed moisture to escape the most efficiently. In the end, we learned that the type of fabric and how closely the fabric is knit, play vital roles in breathability. There was no exact correlation in our testing for Merino wool vs. synthetic materials other than the fact that Merino wool has a much more extensive range of thermoregulation, and is thus a more versatile fabric.

Here we take a training winter run after work with the Smartwool 1/4 Zip in a layered system. After the run where we transitioned from hot to cold  we felt comfortable. This Merino wool competitor thermoregulates well!
Here we take a training winter run after work with the Smartwool 1/4 Zip in a layered system. After the run where we transitioned from hot to cold, we felt comfortable. This Merino wool competitor thermoregulates well!

If you seek a top that will keep you cool while you sweat, the Patagonia Midweight Capilene Crew is our Top Pick. The 100% polyester fabric features a Polartec Power Grid architecture that allows ample air flow. The face fabric is also a little wind resistant making it our go-to for warm, windy day trail runs. It earns a perfect score in this metric for these properties.

A look at the fabric construct of our Top Pick for breathability that allows ample air flow.
A look at the fabric construct of our Top Pick for breathability that allows ample air flow.

The Smartwool 250 ¼ Zip and Smartwool 250 Crew scores a nine out of ten because of its loosely knit fabric design. We also liked how the zip-neck provided additional venting (and warmth) when it was needed. That said, neither breathed as well as the Midweight Capilene, making this top best suited for the warmest days where you might need a long sleeve.

Choose a lightweight material for any of these contenders for an even more breathable base layer.

On the other end of the scale, The North Face Warm Crew and Arc'teryx Rho LT Zip earned the lowest breathability rating. We found that while climbing in Red Rocks and backcountry skiing on Mt. Baker in Washington, it cut the wind and maintained heat well while sitting at the belay or while hanging out on the hill. But when it came to climbing or hiking, it didn't vent moisture as well mostly because of the more wind-resistant face fabrics and thicker design. The Arc'teryx RHO LT Zip proved to be a little more breathable than The North Face Warm. Overall, when performing more aerobic activities like running, nine times out of ten, we had to take it off when the temperature rose in the afternoon. We thought this was perfectly acceptable as most of our running was done on warmer days, and to be expected for most midweight layers.

Hiking uphill in Leavenworth  WA had us pushing the limits of breathability. While the North Face is super warm  it's not the best at breathing  hence hiking without a jacket or extra layer.
Hiking uphill in Leavenworth, WA had us pushing the limits of breathability. While the North Face is super warm, it's not the best at breathing, hence hiking without a jacket or extra layer.

Comfort & Fit


Ah, comfort…something every woman craves. What's better than wrapping yourself in fabrics that are as soft and smooth as Cashmere for everything from on the trail to at-home comfort? When testing this metric, we assessed each top to determine while had the coziest fabrics and the most versatile fits that had us wanting to wear the top day in and day out. In most cases, this testing was the easiest - lazing about watching movies, hanging out around the campfire, going out with friends, and seeing how fabrics feel after day four of constant wear with no wash. In general, we found that Merino wool tops with a fitted, stretchy design did best in this category.


The Coziest Fabrics
Taking home the Top Pick for Everyday Wear is the truly cozy and cuddle-worthy Smartwool 250 Midweight Crew. It features 250g of natural 100% New Zealand merino wool, a bit of stretch, and thicker cuffs and hemlines. It feels glorious against the skin with no itch and simply sheer comfort. Another top-scoring ten out of ten for comfort is the Smartwool Merino 250 ¼ Zip, constructed of the same fabrics but featuring a zip-neck instead of a crew-cut collar. We like wearing the Smartwool 250 Crew each day because of its cute patterns and designs that could be worn on the trail and to work.

The Smartwool 250 Crew is comfortable for wear-all-day (and all-night).
The Smartwool 250 Crew is comfortable for wear-all-day (and all-night).

Other tops like the WoolX Hannah and Icebreaker 260 also have extremely cozy fabrics that will keep you wrapped up on cold days. Of the Merino wool options, the Kari Traa Rose H/Z proves to be the least comfortable 100% Merino wool top that some of our testers claimed to be scratchy when wet.

Fit
When looking at fit, we handed these shirts to a group of women that varied in height and weight. Some were tall while others were short, some had lots of curves, while others had none. In our evaluations, tops that had a stretchier and more voluminous fit proved to be the most versatile. We also looked at the relative lengths of the arms and torso to see which provided the best overall coverage. All shirts proved to be true to fit except the Kari Traa Rose H/Z that we recommend sizing up on.

Check out individual reviews to see the specific fit of each top. In these overviews we provide more depth on the volume of the shirt and points of constriction or discomfort for different body types.

Long Arms and Torso?
Need a shirt with long arms and torso? Luckily we have a host of options. Of synthetic tops, the Arc'teryx Rho LT Zip Neck, a Top Pick for Versatility features super stretchy fabrics that provide a next to the skin fit. The length of both the torso and arms are of some of the longest tested, working for both short and tall ladies, with and without a bust. Of Merino options, we found the WoolX Hannah to have the longest fit. The fabric is somewhat stretchy and fits many of our testers well. In comparison, the Icebreaker 260 Midweight was a little shorter and more ideal for shorter testers in this review.

A look at the length of the Hannah  a great Merino wool option for those with longer arms and/or torso.
A look at the length of the Hannah, a great Merino wool option for those with longer arms and/or torso.

Other longer options: Smartwool Merino 250 1/4 Zip (Editors' Choice), REI Co-op Midweight Base Layer Crew (Best Buy award winner)

The Icebreaker Tech 260 is a great option for those with shorter arms and torso.
The Icebreaker Tech 260 is a great option for those with shorter arms and torso.

Shorter Styles: The North Face Warm Crew, Kari Traa Rose H/Z (deep zip-neck), Icebreaker Tech 260 Midweight

Layering Ability


A good base-layer can easily be worn next to the skin while layering a mid layer or jacket over top. While most long-underwear tops are presumably the "next-to-skin" layer, it is an added bonus when you can wear a tank or tee underneath if you expect conditions to warm up. Not only that, but you want to make sure that you can throw layers over top and remove them without too much effort or static electricity that might cause your shirt to ride up while on the move. During our tests, we looked at the fabric make-up of each top and layered a fleece mid layer overtop to see how easy or hard it was to pull on the mid layer. Long underwear tops that did best in this category feature a slippery face fabric, stretchier and thinner fabrics, and longer arms or thumb loops. Synthetic base layers did better than Merino wool in this category.


Of all tops tested, the Arc'teryx RHO LT Zip proved to be the easiest to layer, earning a solid ten out of ten! The frictionless face fabric slides smoothly against even the fleeciest mid layers like the Patagonia R1 - Women's. The arms are long and can be held when layering to avoid frustrating layering situations like those experienced with more frictiony competitors like the Icebreaker 260 Midweight or WoolX Hannah. Other tops that do well with layering include the 100% polyester REI Co-op Midweight Base Layer because of its frictionless face fabric and super stretchy design that hugs the body. While the North Face Warm does a great job not riding up while in action, the thicker fabric design is harder to layer than those with a thinner construct.

The Smartwool 1/4 zip is a little thinner allowing it to layer a little easier than others. Here we add another layer of warmth during this super cold day at Mt. Baker in Washington state.
The Smartwool 1/4 zip is a little thinner allowing it to layer a little easier than others. Here we add another layer of warmth during this super cold day at Mt. Baker in Washington state.

Of the Merino wool competitors, the Smartwool ¼ Zip and Kari Traa Rose are the easiest to layer, because of the next-to-skin fit and zip neck that offered a more streamlined layering experience. The Kari Traa Rose has a super tight-knit weave that makes sliding layers overtop easier than other Merino wool competitors. If you seek a Merino wool top that is easy to layer, consider a zip-neck option like those recommended above. Otherwise, go for a synthetic option that will leave you a little frustrated with little to no ride-up.

Layering the Hannah is a little harder than other synthetic competitors because of its stickier face fabrics. That said  we enjoy the long arms that allow us to pull them through the mid layer.
Layering the Hannah is a little harder than other synthetic competitors because of its stickier face fabrics. That said, we enjoy the long arms that allow us to pull them through the mid layer.

Synthetic base-layers proved to be easier to layer then Merino wool because of their slipperier face fabrics that don't grab mid-layers and pull.

Drying Speed


In need of a top that dries quickly? If you plan on adventuring in areas where you might encounter precipitation, you may require a quick-drying top. Wear it, take it off, and let it dry on a rock or in your laundry hamper for use the next day. To evaluate this metric, we went hiking in all sorts of precipitation and performed a few tests in the lab. We looked to see which (a) absorbed more water and (b) dried the fastest in a controlled experiment. To do this, we weighed each shirt's dry weight. Then we washed each shirt for 30 minutes. Then we measured the wet weight. After that, we dried each shirt in the dryer at low temperature for ten-minute intervals, weighing each every ten minutes. The shirt that got back to its dry weight proved to be fastest to dry. Overall, we found breathable synthetics to perform better in these metrics.


Synthetics
As expected, the shirts that proved to be more impervious to water typically dried faster. Bringing home a perfect ten in this category, our Top Pick for Breathability, the Patagonia Capilene Midweight proved to be the quickest to dry and absorbed the least amount of moisture (in part to its airy design). It dried in just 40 minutes and only absorbed 1.65oz of water after washing for 30 minutes. This makes it a perfect option for those seeking a layer that will perform for multiple days on end. Other shirts that dried quickly and absorbed little water include the REI Co-op Midweight Base Layer and North Face Warm Crew. BOTH absorbed only 2.15oz of water after washing. However, The North Face, proved to perform a smidgen better, drying in just 50 minutes. The REI Co-op Midweight dried in 60 minutes, similar to the Arc'teryx Rho LT Zip. All these top performers feature a polyester-construct. Those with 100% polyester proved to be faster than those with a hybrid of elastane or spandex materials. All are great options for rainy weather.

This metric looks at the drying speed when not worn. Look at warmth if you want to figure out how quickly fabrics dry out when worn.

Merino Wool
While Merino wool competitors absorbed much more water, we were surprised at their great rate of drying. For example; the Icebreaker Tech 260 is the heaviest contender tester (both dry and wet) but it managed to dry out at a similar time to all Merino wool tops tested (roughly 90 minutes). The only Merino wool top that took a little additional drying time is the Smartwool 250 Crew that took 100 minutes instead of 90 minutes. Of the Merino wool shirts tested, the Kari Traa proved to absorb the least amount of water (2.8oz), making it a great option for wet weather.


Merino wool stays warm when wet, but they don't repel water or dry as quickly as synthetic options. Take a look at the charts below to see how all competitors did comparatively.


Durability


The best base layers out there should last you for multiple years to come. It shouldn't shrink, stretch out, pill, or fall apart after just a few months of use. Most importantly, a durable base layer shouldn't see holes after just a few times out on the trail. With prices ranging from $50 to $125, it's important to know that this shirt should last. To look at durability, we inspected shirts for fly aways, noted quality stitching, and looked for signs of wear and tear. We shimmied through canyons and bushwhacked through forests to see if the fabric snagged or tore.

We also wore heavy backpacks when heading up to the climbing crag or while camping to see if common areas of wear and tear became obvious after just a few months. We also looked to see if any garment shrunk or pilled after washing, and whether or not odors persisted. The best products showed little to no wear and tear, didn't smell, and proved to retain its performance. In our tests, we learned that while Merino wool doesn't smell like synthetic competitors, they were far less durable.


After many years of heavy use, we are super happy with the Arc'teryx Rho LT ¼ Zip. Arc'teryx is known for its bomber craftsmanship and this product is no different. We have used and abused it while climbing, hiking, split-boarding, and more. After many long years of use, there are still no signs of stitching fly-aways or major areas of wear and tear. Our only caveat is that the fabric retains a little smell, earning it a nine out of ten. However, this is easily abolished by a tech-fabric cleanser use every six months.

Other durable synthetic products that showed a little pilling, but performed well overall include The North Face Warm Crew that scored a nine out of ten for its thick fabrics and great durability. The REI Co-op Midweight Crew and Patagonia Capilene Crew also did well, but we observed a little pilling around the stitching seams, earning both a score of eight out of ten. All these top scorers are of polyester design.

The Arc'teryx Rho LT scores a perfect ten for its renowned craftsmanship and wonderful performance!
The Arc'teryx Rho LT scores a perfect ten for its renowned craftsmanship and wonderful performance!

Of the Merino wool contenders, the Kari Traa Rose H/Z proved to be the most durable scoring an eight out of ten. Unlike the Smartwool tops that proved to be the least durable in this review, the Kari Traa Rose features a tightly-knit face fabric that doesn't snag. The fibers are seemingly shorter and have proven to be more durable and a better option for those seeking a base layer that they can use for high-friction sports like canyoneering, bushwacking, or rock climbing.

The Smartwool 250 Crew, on the other hand, proved to be the least durable of all. The fabric pills, the threads come undone, and we even observed a hole in the face fabric. As a result, we're disappointed with the durability of the Smartwool products. If you seek the most durable product out there, be sure to look into a synthetic base layer like the Arc'teryx Rho LT or the merino wool Kari Traa Rose H/Z.

The 250 Crew rubbed a hole through the fabric and experienced stitching flyaways throughout the garment. While this is a super comfortable and cozy shirt  it's not very durable.
The 250 Crew rubbed a hole through the fabric and experienced stitching flyaways throughout the garment. While this is a super comfortable and cozy shirt, it's not very durable.

In our observations over our testing period, we found that our merino wool layers need to be treated a more carefully than their synthetic competitors. We found that fibers in Merino wool products were more conducive to snags and the fabric pilled much easier than synthetics.

A Note on Odor
In all our tests, the synthetic shirts constructed of polyester typically smell more over time than those made of Merino wool. We also found that Merino wool tops could be worn for multiple excursions without washing before odor became an issue. Despite companies efforts to develop odor-resistant fabrics with a polyester design, we found that they inevitably smell over time, whereas Merino wool allows odors to wash away. Some of our testers preferred Merino wool for this one simple fact.

Completing Your Layering System: Long Underwear Bottoms


Long underwear bottoms are a perfect complement to any cold weather layering system. If you plan on participating in any cold weather sport, it's imperative to add base layer bottoms to your "must have" winter gear list to keep you warm and safe. Similar to base layer tops, performance bottoms wick moisture away from your skin effectively keeping you warm when the temperatures dip below freezing.

A look at different types of long underwear bottoms offered. Like long underwear tops  you will find a similar spread of fabrics and weights. Choose from 3/4 and full length options to complement your long underwear top for optimal warmth.
A look at different types of long underwear bottoms offered. Like long underwear tops, you will find a similar spread of fabrics and weights. Choose from 3/4 and full length options to complement your long underwear top for optimal warmth.

Choosing a pair of bottoms is similar to choosing a top: take into consideration the weight of the fabric, the material, and the cut. When looking at fabrics, make sure you check the packaging to ensure there is no cotton and its fabric is composed of merino wool, synthetic, silk, or a blend. The pros and cons for each of these fabrics are the same as we discussed in our Buying Advice guide. For weight, consider the activity you will be participating in to decide what weight to choose.

For example, if you live in Northern Minnesota and plan on hunkering down to ice fish all winter, look at a heavyweight option. If you plan on hiking a lot, choose a lightweight option. Remember that these bottoms are a little different then tops since you won't be able to take them off easily if you're too hot. Last but not least, consider the cut. In general, you can choose from 3/4 and full pant options. Choose a 3/4 length for activities where you might wear high socks like skiing. Choose a long pant option for everything else.

Most long underwear tops have a complementary bottom made of similar materials, often with different cut options. For your shopping ease, we have included these options at the bottom of each individual review.

Conclusion


With so many options out there, it's difficult to determine the best base layer. However, it's important to figure out what you need for the function your shirt should provide. Consider the fabric type, style, and weight. Also, make sure you select a shirt that will fit you best. All contenders in this review work perfectly as apart of a layering system and can be worn on its own as well. Read through our Buying Advice article for more information on the different fabrics and cuts that are available to find the best option for you. Good luck in your search!

Trail running during an after-work run. The Smartwool 1/4 Zip sufficed on this trip providing great thermoregulation.
Trail running during an after-work run. The Smartwool 1/4 Zip sufficed on this trip providing great thermoregulation.
Amber King

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Still not sure? Take a look at our buying advice article for more info.

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