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REI Co-op Underwear

(52 products)

Products (52)

Sort: Best Match

Top Rated
REI Co-opLightweight Half-Zip Base Layer Top - Men's
$44.95
15 reviews with an average rating of 4.5 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular, Big
Top Rated
REI Co-opMidweight Base Layer Crew Top - Toddlers'
$24.95
15 reviews with an average rating of 4.7 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular
Top Rated
REI Co-opMidweight Base Layer Bottoms - Toddlers'
$24.95
8 reviews with an average rating of 4.9 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular
REI Co-opActive Bikini Underwear - Women's
$19.95
53 reviews with an average rating of 3.4 out of 5 stars
Size Type:
Regular, Plus
REI Co-opMerino 185 Base Layer Top - Women's
$69.95
57 reviews with an average rating of 4.2 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular
REI Co-opActive Thong Underwear - Women's
$6.83 - $14.95
24 reviews with an average rating of 4.3 out of 5 stars
Size Type:
Regular, Plus
Top Rated
REI Co-opLightweight Crew Base Layer Top - Men's
$19.93 - $29.95
23 reviews with an average rating of 4.5 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular, Big
Top Rated
REI Co-opHeavyweight Merino Base Layer Half-Zip Top - Women's
$104.95
27 reviews with an average rating of 4.7 out of 5 stars
Underwear Weight:
Heavyweight
Size Type:
Regular, Plus
Top Rated
REI Co-opLightweight Long-Sleeve Crew Base Layer Top - Women's
$27.93 - $39.95
28 reviews with an average rating of 4.6 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular, Plus
REI Co-opEveryday Boxers - Men's
$22.95
131 reviews with an average rating of 4.2 out of 5 stars
Size Type:
Regular, Big
Top Rated
REI Co-opLightweight Base Layer Tights - Women's
$39.95
7 reviews with an average rating of 4.6 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular, Plus
REI Co-opActive Pursuits Crop Tank Top - Women's
$30.93 - $44.95
10 reviews with an average rating of 4.0 out of 5 stars
Bra Support:
Low Impact
Support Style:
Compression
Fabric:
86% recycled polyester/14% spandex (bluesign approved)
Top Rated
REI Co-opMerino 185 Long-Sleeve Half-Zip Base Layer Top - Men's Tall Sizes
$89.95
13 reviews with an average rating of 4.9 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Tall
REI Co-opMerino 185 Base Layer Bottoms - Women's Plus Sizes
$79.95
10 reviews with an average rating of 3.8 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Plus
Top Rated
REI Co-opLightweight Crew Base Layer Top - Women's
$29.95
21 reviews with an average rating of 4.8 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular, Plus
Top Rated
REI Co-opLightweight Half-Zip Base Layer Top - Women's
$44.95
12 reviews with an average rating of 4.7 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular, Plus
REI Co-opActive Bralette 2.0
$34.95
124 reviews with an average rating of 4.3 out of 5 stars
Bra Support:
Low Impact
Support Style:
Encapsulation
Fabric:
86% polyester/14% spandex mesh
REI Co-opMerino 185 Long-Sleeve Base Layer Top - Women's Plus Sizes
$79.95
29 reviews with an average rating of 4.4 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Plus
REI Co-opMerino 185 Long-Sleeve Half-Zip Base Layer Top - Women's Plus Sizes
$89.95
18 reviews with an average rating of 4.3 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Plus
REI Co-opActive Hipster Underwear - Women's
$18.95
38 reviews with an average rating of 3.9 out of 5 stars
Size Type:
Regular, Plus
REI Co-opMerino 185 Base Layer Top - Women's Plus Sizes
$69.95
22 reviews with an average rating of 4.0 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Plus
REI Co-opEveryday Boxer Briefs - Men's
$22.95
159 reviews with an average rating of 4.2 out of 5 stars
Size Type:
Big

31–52 of 52 products

Sort: Best Match

Related Expert Advice articles

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.

Read full article: How to Choose Base Layers

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