Under Armour Heatgear Sonic Fitted Sleeveless T-Shirt - Boys' Grade School The Under Armour Sonic Fitted T-Shirt features the signature moisture transport system that wicks sweat and dries quickly leaving your skin cool and comfortable. The lightweight, four-way stretch design of the fabric provides for added flexibility. UPF 50+ protects your skin from the sun’s harmful rays. Anti-odor technology works to provide long-lasting freshness. HeatGear® is best for weather between 75 and 100 degrees. 84% polyester/16% spandex. Imported.