How to Choose Base Layers
REI Co-op Lightweight Base Layer Bottoms - Men's
$39.95
Members get an est. $3.99 in rewards
A synthetic base layer for moderate temps, the men's REI Co-op Lightweight base layer bottoms keep you dry and comfortable whether you're venturing into the mountains or trekking across open desert.
- Recycled polyester/spandex wicks sweat and dries quickly
- Fabric has a soft and silky feel for next-to-skin comfort
- UPF 50+ sun protection
- Soft, elastic waistband offers a comfortable fit
- Fly opening
- Crotch gusset for easy movement
- Locker loop for hang-drying
- Inseam length: Regular sizes: 28 in.; Tall sizes: 31 in.
- Weight (size M): 5.7 oz.
- Machine-wash warm; wash separately; do not use bleach or fabric softeners; tumble dry low and remove promptly
- Made in a Fair Trade Certified™ factory
- Contains materials that meet the bluesign® criteria
- 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
Imported.
View all REI Co-op Men's Base Layer Bottoms| Best Use | Multisport |
|---|---|
| Fabric | 94% recycled polyester/6% spandex (bluesign approved) |
| Sun-Protective Fabric | Yes |
| UPF Rating | 50+ |
| Moisture Wicking | Yes |
| Quick Drying | Yes |
| Fly Opening | Yes |
| Underwear Weight | Lightweight |
| Inseam (in.) | 28, 31 inches |
| Gender | Men's |
| Sustainability | Contains materials that meet the bluesign® criteria Fair Trade Certified™ factory Contains recycled materials From a Climate Label Certified brand |
REI Co-op Clothing - Men's
| XS | S | M | L | XL | XXL | XXXL | 24 IN Waist | 26 IN Waist | 28 IN Waist | 30 IN Waist | 31 IN Waist | 32 IN Waist | 33 IN Waist | 34 IN Waist | 35 IN Waist | 36 IN Waist | 38 IN Waist | 40 IN Waist | 42 IN Waist | 44 IN Waist | 46 IN Waist | 48 IN Waist | 50 IN Waist | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chest | 35 | 36 - 38 | 39 - 41 | 42 - 45 | 46 - 49 | 50 - 53 | 54 - 57 | |||||||||||||||||
| Sleeve Length | 32 | 32.5 | 33 | 33.5 | 34 | 34.75 | 35.5 | |||||||||||||||||
| Waist | 27.5 | 28 - 30 | 32 - 34 | 36 - 38 | 40 - 42 | 44 - 46 | 48 - 50 | 24 | 26 | 28 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 38 | 40 | 42 | 44 | 46 | 48 | 50 |
| Hip | 33.5 | 34.5 - 36.5 | 37.5 - 39.5 | 41 - 43 | 44 - 46.5 | 47.5 - 50.5 | 51.5 - 54.5 | 32 | 33.5 | 34.5 | 36.5 | 37 | 37.5 | 38.5 | 39.5 | 40.25 | 41 | 43 | 44 | 46.5 | 47.5 | 50.5 | 52.5 | 54.5 |
| Inseam | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 |
Sizing Notes
Measurements are stated in inches unless otherwise indicated. Size chart values represent body measurements, not garment measurements.
SHORT: Some pants are available in short sizes, which generally means an inseam that is 2.5 inches shorter than regular sizes.
TALL: Some pants, shirts, jackets and parkas are available in tall sizes, which generally means an inseam that is 3 inches longer and a rise that is 1 inch longer, a shirt or jacket body that is 2 inches longer, a parka body that is 2.5 inches longer and sleeves that are 2.5 inches longer than regular sizes.
Capri or cropped pants have an intentionally shorter inseam—reference the technical specs instead of this chart.
Inseam is measured to the floor.
Buying Advice
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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.
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Customer Images
Ben T
Received free product
Bend, OR
Comfortable, functional base layer
2 months ago
I have a size large, which fits true to size (note the 28" inseam length description below). This base layer provided good warmth without being bulky, and is very comfortable to wear. The base layer is holding up well to a half-dozen wash/hang dry cycles so far. The only reason I didn't give these base layers a 5/5 stars is because all sizes have an inseam length of 28". This is reasonable given that people typically wear longer socks in situations where they wear base layers, but I often wear 1/4 length socks with a base layer/tights beneath running shorts when running in cooler weather, and so I have some bare leg with my 33" inseam in my size large base layer (which was otherwise a great size!).
Age:35–44
Weight:175–200 lbs.
Height:6'0"
Yes , I recommend this product
PetHenry
Received free product
Seattle, WA
Cyclist likes REI base layer
1 month ago
I'm a cyclist and sometimes I need an extra layer. These bottoms are great if it's cold at the beginning of a ride. They keep me warm but I can easily remove them, even over my cycling shoes, once I warm up. They also stay securely fastened around my waist, unlike other bottoms I've tried. I recommend these!
Age:65–74
Weight:150–175 lbs.
Height:5'6"
Yes , I recommend this product
Mike
Received free product
Los Angeles, CA
Warm, flexible and comfortable
1 month ago
I use these primarily on hiking and overlanding trips as an undergarment. They are flexible but warm (not too warm) and provide an additional layer of protection. They run a little big so be advised at least in my case.
Age:45–54
Weight:200–225 lbs.
Height:5'10"
Yes , I recommend this product
Patm
Received free product
Denver co
Summer thermals
1 month ago
So I got it on the summer so I didn't really get to try the heat aspect of these pants but they fit very well. Medium was a bit large for me so I would order a size down. We will see how these are for this winter.
Age:25–34
Weight:175–200 lbs.
Height:5'11"
Yes , I recommend this product
osidd
Maryland, USA
hiking leggings
2 months ago
I loved the previous version of these base layers, which are one of my hiking essentials - making me nervous about this redesign. After a first day of hiking with them, I'm mostly relieved. The new design is still comfortable for extended wear, but I'd say it's a bit less breathable (old version had visible pores). These may be less comfortable in humid weather. The fit remains comfortable for extended wear- I use these like leggings under gym shorts for trail hiking (solving the chafing, underwear, and overheating problems all in one stroke). But the super-breathable previous version would be even better...
Age:45–54
Yes , I recommend this product
T BONE
Rocky Mountains Colorado
Excellent Product
6 months ago
Great lightweight bottoms. Perfect for spring skiing
Height:5'5"
Weight:125–150 lbs.
Yes , I recommend this product
Jeff C
Salt Lake City, Utah
Great Value & Great Product
6 months ago
I'm super impressed by this product. I own a bunch of other name brand base layers and got this just to use up the rest of a gift card. Couldn't have been more pleasantly surprised. Highly recommend! Super soft and warm.
Height:5'9"
Age:35–44
Weight:150–175 lbs.
Yes , I recommend this product
Jjeff
MN
Very good value and nice base layer bottoms
5 months ago
Very nice base layer bottoms, good value. I like that they came in Talls and no extra cost. Nice fitting and and seems well made and nice material. True to size and not too short or tall of a rise, all in all a decent base layer bottom and nice and lightweight, not too hot.
Height:6'1"
Weight:275–300 lbs.
Yes , I recommend this product
HTC
FINALLY REALLY COMFORTABLE MEN'S LONG UNDERWEAR
4 months ago
Great long underwear bottoms! What I've been looking for a long time. Like old time Patagonia Capilene at half the price and with a wide waist band that doesn't rollover. Better than anything else I've found in the past 10 years!
Keith
Huntington beach
Huge fan of these!
4 months ago
I love these. I really hate that this design is discontinued. The new replacement models are not the same. I wish i could find more of them somewhere else
Age:35–44
Weight:175–200 lbs.
Height:6'0"
Yes , I recommend this product
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