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Underwear

(582 products)

Products (582)

Sort: Best Match

REI Co-opMidweight Long-Sleeve Base Layer Top - Women's
$26.83 - $54.95
262 reviews with an average rating of 4.2 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular, Plus
REI Co-opMidweight Base Layer Tights - Women's
$26.83 - $54.95
100 reviews with an average rating of 4.2 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular, Plus, Petite
Top Rated
REI Co-opMidweight Long-Sleeve Base Layer Top - Men's
$26.83 - $54.95
160 reviews with an average rating of 4.5 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular, Big, Tall
Top Rated
REI Co-opLightweight Long-Sleeve Crew Base Layer Top - Women's
$39.95
24 reviews with an average rating of 4.6 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular, Plus
SmartwoolClassic All-Season Merino Long-Sleeve Base Layer Top - Women's
$66.93 - $90.00
119 reviews with an average rating of 4.4 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular, Plus
Top Rated
Arc'teryxRho LT Crew Neck Base Layer Top - Men's
$100.00
29 reviews with an average rating of 4.8 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular, Big
Top Rated
SmartwoolClassic All-Season Merino Long-Sleeve Base Layer Top - Men's
$44.83 - $90.00
67 reviews with an average rating of 4.6 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular, Big
REI Co-opLightweight Long-Sleeve Crew Base Layer Top - Men's
$29.93 - $39.95
10 reviews with an average rating of 4.3 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular, Big, Tall
REI Co-opMidweight Base Layer Half-Zip Top - Women's
$59.95
152 reviews with an average rating of 4.4 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular, Plus
REI Co-opMidweight Base Layer Bottoms - Men's
$54.95
77 reviews with an average rating of 4.4 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular, Big, Tall
tasc PerformanceElevation Merino Base Layer Bottoms - Women's
$34.73 - $54.73
Save 30% - 56%
compared to $79.00
Members use code OUTFALL25 for $20 off when you spend $100+ at REI Outlet.
57 reviews with an average rating of 4.2 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular, Plus
REI OUTLET
REI Co-opEveryday Boxer Briefs - Men's
$22.95
148 reviews with an average rating of 4.2 out of 5 stars
Size Type:
Regular, Big
REI Co-opEveryday Boxers - Men's
$22.95
121 reviews with an average rating of 4.2 out of 5 stars
Size Type:
Regular, Big
Top Rated
SmartwoolClassic Thermal Merino Crew Base Layer Top - Women's
$81.73
Save 28%
compared to $115.00
Members use code OUTFALL25 for $20 off when you spend $100+ at REI Outlet.
369 reviews with an average rating of 4.7 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular, Plus
REI OUTLET
SmartwoolClassic Thermal Merino Base Layer Bottoms - Women's
$115.00
736 reviews with an average rating of 4.5 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular
Arc'teryxRho Base Layer Bottoms - Women's
$24.83 - $100.00
16 reviews with an average rating of 4.1 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular, Plus
REI Co-opActive Briefs - Women's
$17.95
38 reviews with an average rating of 4.2 out of 5 stars
Size Type:
Regular, Plus
REI Co-opLightweight Base Layer Bottoms - Men's
$39.95
13 reviews with an average rating of 4.2 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular, Big, Tall
Top Rated
REI Co-opMidweight Base Layer Half-Zip Top - Men's
$59.95
150 reviews with an average rating of 4.6 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular, Big, Tall
tasc PerformanceElevation Merino T-Shirt - Men's
$34.73 - $54.73
Save 30% - 56%
compared to $79.00
Members use code OUTFALL25 for $20 off when you spend $100+ at REI Outlet.
39 reviews with an average rating of 4.3 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular, Big
REI OUTLET
Top Rated
SmartwoolClassic Thermal Merino Base Layer Bottoms - Men's
$115.00
619 reviews with an average rating of 4.7 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular, Big
REI Co-opLightweight Half-Zip Base Layer Top - Women's
$44.95
1 reviews with an average rating of 5.0 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular, Plus
Top Rated
REI Co-opMidweight Base Layer Bottoms - Kids'
$16.83 - $34.95
8 reviews with an average rating of 4.6 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular
Top Rated
PatagoniaCapilene Midweight Crew Base Layer Top - Men's
$59.93 - $89.00
79 reviews with an average rating of 4.5 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular, Big
Top Rated
REI Co-opMidweight Crew Base Layer Top - Toddlers'
$24.95
14 reviews with an average rating of 4.7 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular
Top Rated
SmartwoolClassic Thermal Merino Crew Base Layer Top - Men's
$115.00
1506 reviews with an average rating of 4.7 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular, Big
Top Rated
REI Co-opMerino 185 Long-Sleeve Base Layer Top - Men's
$79.95
186 reviews with an average rating of 4.5 out of 5 stars
Underwear Weight:
Lightweight
Size Type:
Regular, Big
REI Co-opActive Hipster Underwear - Women's
$18.95
34 reviews with an average rating of 3.9 out of 5 stars
Size Type:
Regular, Plus
Top Rated
SmartwoolClassic Thermal Merino Crew Base Layer Top - Women's
$115.00
1151 reviews with an average rating of 4.7 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular, Plus
Kari TraaFryd Base Layer Top - Women's
$29.83 - $65.00
24 reviews with an average rating of 4.0 out of 5 stars
Underwear Weight:
Midweight
Size Type:
Regular

1–30 of 582 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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