UA Base 4.0 is built for extreme cold weather and lower activity. It uses a unique pattern that's designed to trap heat without adding bulk. Think long underwear, revamped for today's top athletes. UA Base™ 4.0 Extreme Baselayer is our warmest yet, locking in your body's heat to deliver extreme warmth in the extreme cold UA Scent Control Technology to keep you undetected in all pursuits Soft, brushed grid interior traps air against your skin, closely managing your body's microclimate to keep you warm & comfortable Material wicks sweat & dries really fast 4-way stretch construction moves better in every direction 78% Polyester/22% Elasterell Style #: 1353351 Imported