Classic Thermal Merino Baselayer Bottom - Women's
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Classic Thermal Merino Bottom delivers breathable warmth for winter adventures
What Our Gearhead® Experts Are Saying:
“These baselayers are my go-to when the temps drop below freezing. They’re soft, warm, and never itchy. Even after a full day of touring, they wick sweat like a champ and still smell fresh enough for the après.”
When the air turns crisp and the trail dusts over with frost, we rely on the Smartwool Classic Thermal Merino Baselayer Bottom for unmatched warmth and comfort. Crafted from 100% merino wool, this heavyweight knit regulates temperature naturally—keeping us warm during dawn starts yet breathable when the day heats up.
Merino’s soft, itch-free fibers wick moisture away and resist odors, making these bottoms perfect for back-to-back ski days or multi-day winter treks. The interlock knit enhances stretch and durability, while flat merrow seams and a merino-lined waistband prevent chafing for all-day ease. Whether layering under ski pants or wearing solo at camp, this baselayer keeps us cozy, dry, and ready for anything the cold brings.
Details
- Warm merino baselayer bottom for winter hikes and ski days
- 100% merino wool provides natural temperature regulation
- Soft interlock knit adds stretch and structure for lasting comfort
- Moisture-wicking and odor-resistant fibers keep you fresh longer
- Flat seams and elastic waistband reduce friction and irritation
- Slim fit layers easily under shells or snow pants
- Item #SWL01F3
- Material
- 100% merino wool
- Insulation Weight
- midweight (250gm)
- Fit
- slim
- Style
- tights
- Anti-Odor
- natural attribute of merino wool
- Claimed Weight
- 7.3oz
- Activity
- ski, snowboard
- Manufacturer Warranty
- 2 years
Reviews
Q&A
Overall Rating
4 based on 23 ratings
Review Summary
Fits True To Size
Screen reader users: the following list provides a visual scale to illustrate the product fit. Please refer to the heading above for the fit type in text.Customer Images
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Selecting an option will reload the available reviews on the pageMarch 3, 2026
Not durable
- Familiarity:
- I've used it several times
The seams on these thermal bottoms started unraveling after the second wash. I own other wool items and I know how to wash them and to not put them in the dryer so having these fall apart so fast was disappointing.
Originally reviewed on Backcountry.com
December 23, 2025
Fist time having thermals
- Familiarity:
- I've used it several times
I bought these thermals for a trip in upstate NY and they hold up pretty well. I know wear them casually on frigid days and they word very well. The Merino wool seems to get a littel scratchy the more you throw it in the wash though.
Originally reviewed on Backcountry.com
November 29, 2025
Never seen a cold sheep
- Familiarity:
- I've put it through the wringer
If you're planning any travel above 60 degrees north latitude in the winter, plan to bring along your Smartwool thermals. You'll be glad you did. The Smartwool products are more durable than any other merino wool products that I have tried. I have worn the thermals under a dry suit in icy cold rivers and under my clothing on land. I love the comfort.
Originally reviewed on Backcountry.com
January 7, 2025
Keeps You Warm When It's Cold Outside
- Familiarity:
- I've used it several times
I wore these for a couple runs when our temps dropped under 20. Very comfortable and wind resistant.
Originally reviewed on Backcountry.com
January 7, 2025
Warm but didn't last
- Familiarity:
- I've used it once or twice and have initial impressions
Seems didn't last. Super warm and worn a few times while adventuring with littles but the seems in multiple spots came unraveled.
Originally reviewed on Backcountry.com
December 29, 2024
I’m a dude, and it looks great on me
I want pink, but they didn’t have that in men’s. I’m 5’8, 165 pounds, and I bought an XL, which is a little bit baggy so I would probably get a large next time.
Originally reviewed on Backcountry.com
November 19, 2024
Super warm thermal leggings!
- Familiarity:
- I've used it once or twice and have initial impressions
Bought these to have for when it is cold and to keep me warm when camping during winter. I did a lot of research before I purchased these. They are pricey, but worth it. First of all they are thicker and the fit is perfect. They are also flattering and not so thin which allows me to wear them as normal winter leggings as well. Also as pjs around the house during winter too. I loved them so much I decided to buy two more pairs and the base layer tops to match. If you are able to afford these and want thermal base layers that last then these I highly recommend. I’m 5’6, weigh 133 lbs, 30 inch lower waist and a medium fits me perfect.
Originally reviewed on Backcountry.com
September 15, 2024
True to size
- Familiarity:
- I've used it several times
They are high waisted and true to fit. I'm a curvy woman and they fit very comfortably. I wore these under my jeans in Japan in January. They kept me warm and they are oder repellent which is nice while traveling. Highly recommend.
Originally reviewed on Backcountry.com
April 9, 2024
In love!
- Familiarity:
- I've put it through the wringer
I usually struggle to find the perfect fit in bottom base layers, but I was pleasantly surprised to find these fit like a glove right out of the box. I have a bigger bum and run into the issue of layers either being too snug at the waist or too loose at the thighs, but I did not run into this issue at all with these. I wear them casually after a day on the slopes as well and can absolutely see myself wearing them camping, hiking, and in just about any outdoor scenario where the temps drop!
Originally reviewed on Backcountry.com
April 4, 2024
Low rise
The fabric is nice. Unfortunately these are low rise and definitely made for someone with a flat butt. Nice and long though which is what I like. Couldn't keep them though due to that low rise.
Originally reviewed on Backcountry.com
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