Under Armour Boys' HeatGear Armour Up Long Sleeve 90% Polyester/10% Elastane Imported Fitted: Next-to-skin without the squeeze HeatGear fabric is ultra-soft & smooth for extreme comfort with very little weight 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