Under Armour Big Boys' Alter Ego Fitted Shirt Polyester/Elastane HeatGear fabric is ultra-soft & smooth for extreme comfort with very little weigh. 4-way stretch fabrication allows greater mobility in any direction. Moisture Transport System wicks sweat & dries fast. Anti-odor technology prevents the growth of odor causing microbes. UPF 30+ protects your skin from the sun's harmful rays