UA Base™ 2.0 is built for cold weather and high activity levels. 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™ 2.0 Active Baselayer is lightweight, flexible & breathable for high activity in cool conditions. Soft, brushed grid interior traps air, managing your body's microclimate to keep you warm & comfortable. Material wicks sweat & dries really fast. 4-way stretch material moves better in every direction. Dropped, shaped hem. Raglan sleeves. 71% Polyester/29% Elastarell.