Under Armour Heatgear Sonic Fitted 4" Shorts - Boys' Grade School The Under Armour HeatGear Sonic Fitted Short features the signature moisture transport system that wicks sweat away and dries quickly leaving your skin cool and comfortable. The lightweight, four-way stretch fabric design offers flexibility. Anti-odor technology provides long-lasting freshness. HeatGearŪ is best for weather between 75 and 100 degrees. 84% polyester/16% spandex. Imported.