Under Armour Heatgear Sonic Fitted S/S T-Shirt - Boys' Grade School The Under Armour Sonic Fitted T-Shirt features signature moisture transport system that wicks sweat away keeping you cooler and drier. The lightweight, four-way stretch fabric offers added flexibility. UPF 50+ protects your skin from the sun’s harmful rays. Anti-odor technology provides freshness. HeatGear® is best for weather between 75 and 100 degrees. 84% polyester/16% spandex. Imported.