These aren't your grandpa's long underwear. UA took the thermal and rebuilt it to work for athletes that take their game off-road. The unique negative grid traps monster warmth without adding excess weight and the smooth exterior allows easy layering. UA Base 3.0 is heavyweight protection in a lightweight layer. It provides superior warmth for times when you know you'll need it. On the hill or on the move, when you run cold get the UA thermals that keep you going strong.