The original Under Armour HeatGear Longsleeve Thermal Underwear developed for on-field use and still our most recognizable trademark on gameday. Our signature compression fit enhances moisture transport and bolsters muscle support. Durable, abrasion-resistant, full-coverage protection throughout any game or workout. UPF 30+ for protection from harmful sun rays. 81% PolyArmour / 19% Elastene. Imported.