100% Polyester Imported Ready for any workout, the Under Armour Heatgear Armour Compression Sleeveless is the layer you put on first and take off last. It's tight to wick away sweat and quick-drying to keep you cool. No athlete can go without it. HeatGear fabric, with all the benefits of UA Compression, comfortable enough to be worn all day. Stretch-mesh underarm panels deliver strategic ventilation. UPF 30 protects your skin from the sun's harmful rays. 4-way stretch construction moves better in every direction.