Base Layer and Underwear

Smartwool Men's Classic Thermal Merino Base Layer Pattern Crew Boxed Black Mountain Scape

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

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

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

This RedHEAT ACTIVE base layer bottom lives up to its name with optimal body temperature regulation. The innovative technical fabric incorporates carbon microcrystals that store body heat while its microporous structure maintains breathability for maximum

This new RedHEAT EXTREME base layer bottom lives up to its name with optimal body temperature regulation. The innovative technical fabric stores and manages body heat through carbon microcrystals for maximum comfort in extreme conditions. Thanks to the Re

ACTIVE SPORT ankle-length base layer bottom. Elastic waistband. Men ACTIVE style.

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.

The targeted insulation and ventilation in the Men’s Merino 250 Base Layer Bottoms allow you to stay comfortable while you’re out working up a sweat.