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Smartwool Merino 150 Base Layer Bottoms - Women's Review

This lightweight bottom features a merino wool blend offers amazing thermoregulation and durability.
Top Pick Award
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Price:  $80 List | $55.99 at REI
Compare prices at 3 resellers
Pros:  Durable, strong wicking power, comfortable features, cute color options
Cons:  Not very warm
Manufacturer:   Smartwool
By Amber King ⋅ Senior Review Editor  ⋅  Nov 20, 2019
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74
OVERALL
SCORE


RANKED
#6 of 10
  • Warmth - 30% 4
  • Breathability - 30% 10
  • Comfort and Fit - 30% 8
  • Durability - 10% 8

Our Verdict

The women's Smartwood Merino 150 Bottom is a great option if you simply seek a wicking layer that sits next to the skin. Constructed of 87% merino wool and 13% nylon, these base layer bottoms offer amazing wicking power and work well underneath an insulated system. While they aren't very warm themselves, this makes it easy to stack thicker layers on top, to help keep you warm. The synthetic fibers make them more durable and faster to dry out than other 100% wool contenders. If lightweight and durable performance are what you seek, this is a base layer bottom to consider. Wear it during high aerobic days under an insulated system in the winter, or on its own in the summer.


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Pros Durable, strong wicking power, comfortable features, cute color optionsAll season wear, breathable, will keep you dry, warm, improved fitFleece lining is comfortable, elastic fit, amazing value, cute style, very durable, power wicking.Durable, wide range of thermoregulation, comfortable, cute colors.Durable, quick to dry, breathable, warm, high value.
Cons Not very warmLacks durability when worn aloneHigh water absorption.Not super duper warmFabric holds moisture, not the most comfortable against the skin
Bottom Line This lightweight bottom features a merino wool blend offers amazing thermoregulation and durability.A versatile merino wool bottom for year round use.Our favorite bottom with a fleece-lined interior and versatile performance.This is one of the most durable merino wool contender out there.A highly breathable and comfortable synthetic base layer for a great price.
Rating Categories Merino 150 Base Layer Bottoms Merino 250 Bottoms Rho LT Bottoms 200 Oasis Leggings Capilene Midweight Bottoms
Warmth (30%)
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Breathability (30%)
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Comfort And Fit (30%)
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Specs Merino 150 Base... Merino 250 Bottoms Rho LT Bottoms 200 Oasis Leggings Capilene Midweight...
Material 87% Merino wool, 13% nylon core 100% merino Torrent fleece (84% polyester, 16% elastane) 100% merino 5.2-oz (176-g) Polartec® Power Grid® 97% polyester
Fabric weight (g/m²) & relative level of thickness 150 g/m² (lightweight) 250 g/m² (midweight) 150 g/m² (midweight) 200 g/m² (lightweight) 176 g/m² (midweight)
Measured Weight 5.2 oz 7.3 oz 5.8 oz 5.7 oz 6.2 oz
Fabric weights availiable Lightweight (150), midweight (250) Lightweight (150), midweight (250) Lightweight & midweight (AR) options Midweight Cooweight, Midweight, Thermal Weight
Cuts avaliable Full length 3/4 length, full length, onsie (full body w/ hood) Full length 3/4 length, full length Full length
Smelly over time? No No No No Yes
Odor control fabric Naturally odor resistant Naturally odor resistant Polygiene anti-odor finish Naturally odor resistant Polygiene permanent odor control

Our Analysis and Test Results

The Smartwool Merino 150 Bottom is an amazing thermoregulator with powerful wicking power. It functions well underneath a mid-layer and jacket in the winter, or as a standalone piece in the summer. We also love to wear it while on running missions in the shoulder season. It's durable, doesn't stink, and is lightweight. As a result of its great performance, it earns an award as our favorite lightweight long underwear bottom. If you seek a layer that'll wick away your sweat without the insulation, this one should most definitely be considered.

Performance Comparison


The Smartwool 150 is a lightweight option that is perfect for warm to cool weather. Constructed of a merino wool blend  it provides great wicking and breathability for all-day wear.
The Smartwool 150 is a lightweight option that is perfect for warm to cool weather. Constructed of a merino wool blend, it provides great wicking and breathability for all-day wear.

Warmth


Built with 150-grams of insulation, this merino wool-synthetic blend doesn't offer much in the way of insulation.


While the fibers themselves are pretty warm for the lower density it is built with, these bottoms are a far lighter pant than other merino wool contenders. We love to wear it in a layered system. It slides easily under a pair of snow pants or soft pants. If you plan on skiing or hiking with these pants, it's perfectly suited. The material thermoregulates well to keep moisture off the skin. It's just important to ensure that the upper layer has ventilation.

Getting ready to descend into the Ouray Ice Park for some ice smashing. Here we wear the Smartwool 150 layered nicely underneath our soft pants. These pants have a little fleece insulation which makes these base layer bottoms perfect for this activity.
Getting ready to descend into the Ouray Ice Park for some ice smashing. Here we wear the Smartwool 150 layered nicely underneath our soft pants. These pants have a little fleece insulation which makes these base layer bottoms perfect for this activity.

If you're planning on sitting around on ski lifts though, the insulation might be too thin for the coldest days. In that case, we wouldn't recommend it with just a shell of a pant, but make sure to have an insulated snow pant overtop, so your butt doesn't get too cold. If you're going to be trudging uphill, open the vents on your pants and let these bad girls breathe! They truly are suited better for aerobic activities in cold weather or one their own in warm weather. However, you can wear them in super cold weather, but only with a well-insulated system overtop.

The thinner fabrics make this piece a little less warm  and a great option to wick away sweat. The thinner make-up of the merino wool also does good work to insulate while on the go.
The thinner fabrics make this piece a little less warm, and a great option to wick away sweat. The thinner make-up of the merino wool also does good work to insulate while on the go.

Overall, this is far from the warmest base layer bottom we've tested. In fact, it is one of the thinnest. That said, because it wicks so well, it'll offer great warmth, given the upper layer you wear has sufficient ventilation.

Breathability


As a lightweight design, it does an awesome job breathing while out on the trail. We used them snow hiking, backcountry skiing, skiing at the resort, sailing, and ice climbing.


During our adventures, this layer continued to provide all the thermoregulation that we required. When sweating up a storm while trudging uphill over snow, we opened our jacket, and this base layer moved moisture easily away from our skin and out into the air.

Here we ride out big open glaciers in Alaska. Wearing the Smartwool 150 makes it easy to hike up without building up moisture in the material.
Here we ride out big open glaciers in Alaska. Wearing the Smartwool 150 makes it easy to hike up without building up moisture in the material.

When ice climbing, it offered the wicking warmth that we needed going from high-intensity work on the wall, to simply chilling out at the base of the cliff. The key here is that the upper layer needs to ventilate. When that layer wasn't able to vent out the moisture moved from the layer, we'd eventually start sweating, which is something you want to avoid. In comparison to thicker layers, this one does the best of making us sweat the least.

A lightweight and breathable contender.
A lightweight and breathable contender.

On a warm day, it's a great option to wear underneath a breathable shell. The integrated nylon provides exceptional wicking capabilities while the merino wool provides insulation. In our water and drying tests, it absorbed a moderate amount of water and dried at an average rate of speed. As a result, we're happy to report that we'd recommend this bottom for everything from a morning run to an extended backpacking trip into the backcountry. Not only will the fabric wick and breath well, but it will dry out quickly on the trail.

Comfort and Fit


This isn't the coziest of base layers, but it offers nice comfort that feels good to lounge around in.


The integration of the synthetic fibers doesn't feel scratchy or uncomfortable on the skin, but soft and cozy. The thinness of the fabric allows air to flow through the material, so if you're sitting in a cold cabin somewhere in the woods, it's not going to insulate and make you feel ultra-cozy like other contenders with thicker fabrics.

Front...it doesn't have the cleanest fit and constricts around the groin  however  it does feel comfortable on.
Model is 5'6" and 140 lbs. A good length  but could be a touch longer.
A look at the overall fit of the 150 Merino Bottoms by Smartwool
A look at the overall fit of the 150 Merino Bottoms by Smartwool

While on the trail, we appreciate that you can easily wear this base layer next to the skin without a problem. The materials stretch nicely, providing coverage for women of all shapes and sizes. Also, the elastic around the ankle isn't constricting in any way, while it provides a diverse fit for all women.

The fit is true to size. Based on the season, there are different colors and sizes that come out. So be sure to look for those great patterns. The elastic band around the waist isn't insulated but covers a broad section of skin, which offers a nice comfort. It's also not too tight. Overall, we appreciate all the comfort features it has to offer, making it a nice choice for wearing from the ski hill and back into the cabin without a problem.

The Smartwool 150 earns a Top Pick for its lightweight construction that is built with both synthetic and merino wool fibers. It's more durable than other merino wool contenders with impeccable breathability.
A good amount of length around the ankles is great for taller and shorter ladies. The cuffs are also elastic  offering a decent fit for a variety of sizes. We also long the cozy elastic band that sits comfortably on the waist.
A good amount of length around the ankles is great for taller and shorter ladies. The cuffs are also elastic, offering a decent fit for a variety of sizes. We also long the cozy elastic band that sits comfortably on the waist.

Durability


This is one of the most durable merino wool options out there. Integrating a small amount of synthetic fibers, the fabrics retain their shape, even when wet, providing great stretch. After testing it for two years, we still don't see any issues with the fabric.


When running through dense underbrush, the fabric didn't snag and stayed nicely intact. That said, because it is merino wool, we suspect it is not as durable as a 100% synthetic contender because of the properties of the materials. The materials after these two years atiny bit frayed, be we are surprised at how durable this lightweight contender is.

Value


While it might seem expensive, this is a well priced long-underwear bottom. The synthetic integration with the merino wool offers powerful wicking power and thermoregulation. The materials are more durable, so the investment should last a bit longer. Those that will see the most value in it will either be women that run pretty warm (they sweat a lot while exercising) or for those that need a thinner baselayer for skiing uphill, hiking in the woods, or while climbing in the alpine. We think there is a lot of value in this long underwear bottom.

We test this base layer while backpacing in the Faroe Islands. In this cold  wet weather  it's perfect for layering underneath other upper layers that are heavier.
We test this base layer while backpacing in the Faroe Islands. In this cold, wet weather, it's perfect for layering underneath other upper layers that are heavier.

Conclusion


The Smartwool Merino 150 Base Layer Bottoms - Women's is a super-thin synthetic-merino wool pant that offers amazing thermoregulation. It's our favorite for high-intensity missions in the winter or as a thin protective sun layer in the summer. Use it for any mission where you simply need a layer that wicks away moisture and doesn't provide a whole lot in the form of insulation. Oh yeah, it's also been ultra-durable for us in our two years of testing experience.


Amber King