REI Co-op Merino Midweight Base Layer Bottoms - Men's

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Soft, moisture-wicking 100% merino wool makes the men's REI Co-op merino midweight base layer bottoms an ideal next-to-skin layer for high-performance activities in cold weather.


  • Ultra-fine 200g merino wool offers a soft feel without the scratchiness
  • Merino wool naturally wicks away sweat and resists odors
  • Low-bulk flat seams help prevent chafing
  • Crotch gusset allows full range of movement
  • Wide elastic waistband has a low profile so it's comfortable under other layers
  • Designed to hug the body for optimum performance


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

Technical Specs

Best Use



Merino wool

Moisture Wicking


Quick Drying


Fly Opening


Underwear Weight





Fair Trade Certified™ factory

From a Climate Neutral Certified brand

Size Chart

XSSMLXLXXLXXXL24 IN Waist26 IN Waist28 IN Waist30 IN Waist31 IN Waist32 IN Waist33 IN Waist34 IN Waist35 IN Waist36 IN Waist38 IN Waist40 IN Waist42 IN Waist44 IN Waist46 IN Waist48 IN Waist50 IN Waist
Chest3536 - 3839 - 4142 - 4546 - 4950 - 5354 - 57
Sleeve Length3333.53434.53535.7536.5
Waist27.528 - 3032 - 3436 - 3840 - 4244 - 4648 - 502426283031323334353638404244464850
Hip33.534.5 - 36.537.5 - 39.541 - 4344 - 46.547.5 - 50.551.5 - 54.53233.534.536.53737.538.539.540.2541434446.547.550.552.554.5

Sizing Notes

Measurements are stated in inches unless otherwise indicated.

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.

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