Under Armour Men's UA ColdGear Infrared Armour Compression Crew ColdGear Infrared technology uses a soft, thermo-conductive inner coating to absorb and retain your own body heat Dual-layer fabric with an ultra-warm, brushed interior and a slick, fast-drying exterior Engineered with closed-hole mesh zones allow greater breathability where you need it Stretch-mesh underarm panels provide strategic ventilation 4-way stretch fabrication allows greater mobility in any direction