HeatGear is our original performance baselayer—the one you put on first and take off last. So we made it extra comfortable by wicking sweat and stretching so you can move. No athlete can go without it. Super-light HeatGear fabric delivers superior coverage without weighing you down. Stretch-mesh back & side panels deliver strategic ventilation. Material wicks sweat & dries really fast. Generous dropped armholes for full range of motion. Body: 90% Polyester/10% Elastane, Mesh: 92% Polyester/8% Elastane. 90% Polyester/10% Elastane.