ColdGear Infrared lining uses a soft, thermo-conductive inner coating to absorb & retain body heat Dual-layer fabric with an ultra-warm, brushed interior & a smooth, fast-drying exterior 4-way stretch material moves better in every direction Material wicks sweat & dries really fast ColdGear Infrared technology holds in body heat, without adding weight or bulk. It's a special, soft print on the inside and it keeps you warmer, longer, so you can work out in the bitter cold.