REI Co-op Heavyweight Merino Base Layer Bottoms - Women's

View the 18 reviews with an average rating of 4.6 out of 5 stars

$99.95

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Get ready for adventures in the cold with our warmest merino base layer bottoms yet. Made with 100% merino wool, the women's REI Co-op Heavyweight Merino base layer bottoms are supersoft on the skin.

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Heavyweight 250 g merino wool offers a soft feel without the scratchiness
Made with 100% merino wool that naturally wicks away sweat, resists odors and dries quickly
UPF 50+ sun protection
Soft jacquard waistband is comfortable on the skin—and its low profile allows for easy layering
Crotch gusset is made for ease of movement
Close-to-body fit for optimum performance
Weight for size S: 7.6 oz. (216 g)
Locker loop makes it easy to hang these to dry or just keep them off the ground
Machine wash cold, use wool wash product, do not twist or wring, remove promptly; do not bleach; tumble dry low
REI Co-op brand is certified to The Climate Label; we actively fund efforts to reduce carbon emissions across our business and support climate projects around the world
Made in a Fair Trade Certified™ factory

Imported.

View all REI Co-op Women's Base Layer Bottoms

Best Use	Multisport
Fabric	100% merino wool
Sun-Protective Fabric	Yes
UPF Rating	50+
Moisture Wicking	Yes
Quick Drying	Yes
Underwear Weight	Heavyweight
Inseam (in.)	29 inches
Gender	Women's
Sustainability	Fair Trade Certified™ factory From a Climate Label Certified brand

REI Co-op Clothing - Women's

	XXS	XS	S	M	L	XL	1X	2X	3X	0	2	4	6	8	10	12	14	16	18W	20W	22W	24W	26W
Numerical Size	00	0-2	4-6	8-10	12-14	16	18	20-22	24-26	0	2	4	6	8	10	12	14	16	18	20	22	24	26
Bust	31	32-33	34-35	36-37	38.5-40	41-42.5	43-45	47-49	51-53	32	33	34	35	36	37	38.5	40	42.5	45	47	49	51	53
Sleeve Length	29.5	30	30.5	31	31.5	32	32.5	33.5	34.5	30	30	30.5	30.5	31	31	31.5	31.5	32	32.5	33.5	33.5	34.5	34.5
Waist	24.5	25.5-26.5	27.5-28.5	29.5-30.5	32-33.5	34.5-36.5	37.5-39.5	40.5-42.5	44.5-46.5	25.5	26.5	27.5	28.5	29.5	30.5	32	33.5	36	38.5	40.5	42.5	44.5	46.5
Hip	34	35-36	37-38	39-40	41.5-43	44-46	47-49	50-52	54-56	35	36	37	38	39	40	41.5	43	45.5	48	50	52	54	56
Inseam	31	31	31	31	31	31	31	31	31	31	31	31	31	31	31	31	31	31	31	31	31	31	31

Sizing Notes

Measurements are stated in inches unless otherwise indicated. Size chart values represent body measurements, not garment measurements. Some women's pants are available in petite and tall sizes. Typically petite sizes fit women 4'11" to 5'3". Regular sizes fit women 5'4" to 5'8". Tall sizes fit women 5'9" to 5'11".

PETITE: Generally, as compared to regular sizes, petite sizes are 2.5 inches shorter in inseam, 1 inch shorter in body length, 1.25 inches shorter in sleeve length and ¾ inch shorter in total rise.

TALL: tall sizes are 3 inches longer in inseam, 2 inches longer in body length, 2.5 inches longer in sleeve length and 1.25 inches longer in total rise.

Capri or cropped pants have an intentionally shorter inseam—reference the technical specs instead of this chart.

Inseam is measured to the floor.

How to Choose Base Layers

What material is best?

Wool is moisture-wicking and odor-resistant, while synthetic fabrics are more durable and less expensive.

Match the temp to the trek

Lightweight layers are best for moderate to cool temperatures. Midweight layers are best for cold temperatures. Heavyweight layers are best for below-freezing temperatures.

Find your fit

To be able to wick sweat efficiently, your next-to-skin layer needs to actually be next to your skin. A comfortably snug fit everywhere is your goal.

More expert advice

What to Wear Hiking

Layering Basics

Close up of someone that has fallen in the snow and is laughing about it.

How to Choose Insulated Outerwear

From feedback to field testing, all of our gear is dialed-in by REI Co-op members. Their adventures informed every stitch and detail—making for better, longer-lasting gear.

Ratings Snapshot

Product Rating

4.6

View the reviews with an average rating of 4.6 out of 5 stars18 Reviews

10 out of 12 (83%) reviewers recommend this product

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Sarah

Received free product

Vermont, USA

Rated 5.0 out of 5 stars

7 months ago

These are excellent base layer bottoms and are a great value. I live in Vermont where it can be quite cold, and I spend a lot of time doing active things outdoors in the cold. I tested these base layers under my normal jeans, sweat pants with snow pants, and alone to bed. I found them to be extremely warm and comfortable, even when I warmed up and sweated a bit - quick to dry and not itchy when damp. The fabric has a nice weight to it, with medium stretch. I really appreciate the contour sewn into the top of the pants - room for movement in the hips, crotch, and butt. This little bit of extra room, when compared to a straighter cut without the extra contour is why I think they are so comfortable. The waist band is also nice - soft on your skin but holds the pants up well. I typically have a lot of difficulty with any snug fitting pant, from jeans to leggings, riding down as I walk around. This is extremely annoying and is an even bigger problem with base layers because they are under additional layers so I have to go under several layers of pants to pull them up. These do not ride down at all, even during active wear. An extra bonus feature is a small loop to hang the pants to dry. This is awesome because how often do you travel or camp and want to rinse your base layers but need a good way to hang them without a line? Nice feature so I won't hang them over a branch and stretch them out in a weird way.

Age:35–44

Weight:125–150 lbs.

Height:5'4"

Yes , I recommend this product

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Runner19

Received free product

Rated 5.0 out of 5 stars

8 months ago

This is a comfortable, warm, and functional layer for cold weather activities. These looked large but they fit just right--looser than leggings but still form fitting and easy to wear under other pants. They are also long and high waisted, which I like as a bottom layer. The merino wool is not scratchy/itchy. They can be worn on their own but I prefer them as a layering piece, because I prefer softer material as a standalone piece. Very comparable to other, more expensive brands. Highly recommend!

Height:5'5"

Yes , I recommend this product

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cleigh7

Received free product

Midwest

Rated 5.0 out of 5 stars

7 months ago

Super comfortable! I liked the fabric as soon as I put them on, with a good amount of stretch for activity. I wore them under one other layer of sweatpants on morning walks between 20 and 30 degrees with minimal cold issues. Washed in cold water, hung up to dry and no changes in the fabric or stretch.

Age:35–44

Weight:175–200 lbs.

Height:5'7"

Yes , I recommend this product

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RCSull

Received free product

Connecticut

Rated 4.0 out of 5 stars

7 months ago

These definitely have kept me warm on chilly days outside. I have used them for outdoor chores (raking and gardening) and walks around the neighborhood. Being that they are dark in color i have warn them on their own without layering on top. Thermal leggings that actually stay in place. I am rating 4/5 because the material could be softer, but they serve the primary purpose of warmth.

Age:35–44

Weight:150–175 lbs.

Height:5'6"

Yes , I recommend this product

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INW Hiker

Received free product

Rated 4.0 out of 5 stars

8 months ago

Very comfy, soft and warm. The crotch area is a little bigger for me and baggy. I would like them to be a tad longer but won’t keep me from wearing them. They work great as standalone base layer or under hiking pants.

Age:25–34

Weight:125–150 lbs.

Height:5'9"

Yes , I recommend this product

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Alex

Received free product

Washington, DC

Rated 4.0 out of 5 stars

7 months ago

I used these as a base layer during biking in winter in DC - we've had a cold start and they definitely provided the warmth I needed underneath my pants. I love that they are 100% merino which can be hard to find. They do have a very slight itch to them, but it is not problematic, and I suspect it will diminish with a few washes. I ordered a L based on the size chart and as you can see in the pic there is a bit of room - not skin tight. I am 4'11" and 137 lbs.

Age:35–44

Weight:125–150 lbs.

Height:Shorter than 5'

Yes , I recommend this product

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oaklinds

Kansas City, MO

Rated 5.0 out of 5 stars

10 months ago

While I haven't tried these out in the cold yet, I purchased these for an upcoming camping trip and can speak to the quality and fit. I own both Smartwool and now REI Co-Op merino items, and have to say the weave and weight is very similar to SW's classic merino layers. These seem well-constructed. The fabric itself is somewhat itchier compared to SW, but that may change with wear and wash. Seams are flat lay so no digging in; the waist band might not be for everyone (similar to Nike tights) but I didn't mind it. Didn't dig in and I can fold it over if I don't want quite a quite-so-high rise. As for shape, I actually prefer the fit of these to SW's base layer tights—the pattern has a feminine cut to it that works on my body type. I am 5'7", typically a size 4, 34-27-38, and the size Small worked best for me. Fitted but not too snug. Overall, I'm excited to use the heck out of them and see how they hold up. Glad to have an alternative to SW that is slightly cheaper.

Age:35–44

Weight:125–150 lbs.

Height:5'7"

Yes , I recommend this product

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KS18

Oregon

Rated 2.0 out of 5 stars

8 months ago

Was a gamble ordering these since it's merino wool, but they're definitely itchy for me. A bummer since they fit great, I love the higher waist, and are comfy (except for the constant slight itch). Will be returning.

Age:25–34

Weight:150–175 lbs.

Height:5'5"

No, I do not recommend this product

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Joy H

Murrieta

Rated 5.0 out of 5 stars

7 months ago

I didn’t want to like them so much because they aren’t cheap. But I LOVE them. I bought them for the cyber week sale price and I’m super happy. They’re very layerable and lightweight. They’re breathable and I have yet to wear them in the cold but they do have merino wool in them so I’m sure they’ll be warm. I am plus size and they fit me perfectly. I got my size recommended by the size chart and they’re stretchy so if you want a more fitted feel I would size down.

Age:25–34

Weight:225–250 lbs.

Height:5'0"

Yes , I recommend this product

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Amanda

Received free product

Nashville, TN

Rated 5.0 out of 5 stars

8 months ago

These are super comfy. They are form fitting without being too tight. I like how they are a high rise fit with plenty of breathability. I wear these around the house as my cozy pants. I think they are true to size but if you want a tighter fit then maybe size down.

Age:35–44

Weight:125–150 lbs.

Height:5'4"

Yes , I recommend this product

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REI Co-op Heavyweight Merino Base Layer Bottoms - Women's

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Features

Technical Specs

Size Chart

Sizing Notes