Base Layer and Underwear

This lightweight RedHEAT ACTIVE men's base layer crew neck top lives up to its name with optimal body temperature regulation. The innovative technical fabric of our men’s thermal base layer incorporates carbon microcrystals that store body heat, while its

This lightweight RedHEAT ACTIVE men's base layer zip top lives up to its name with optimal body temperature regulation. The innovative technical fabric of our men’s thermal base layer incorporates carbon microcrystals that store body heat, while its micro

Smartwool Smartwool Men's Classic Thermal Merino Base Layer 3/4 Bottom Boxed Black

Smartwool Smartwool Men's Classic Thermal Merino Base Layer 1/4 Zip Boxed Deep Navy

Smartwool Smartwool Men's Classic Thermal Merino Base Layer Colorblock Crew Boxed Deep Navy/Laguna Blue

Smartwool Smartwool Men's Classic Thermal Merino Base Layer Crew Boxed Charcoal Heather

Smartwool Smartwool Men's Classic Thermal Merino Base Layer Crew Boxed Laguna Blue Heather

Smartwool Smartwool Men's Classic Thermal Merino Base Layer Crew Boxed Acorn Heather

Our best-selling base layer bottoms made from soft and breathable 100% merino wool jersey, the 200 Oasis Leggings are the perfect foundation for your cold-weather layering.