Under Armour Men's HeatGear Armour CoolSwitch Supervent Sleeveless Shirt 84% Polyester/16% Elastane Imported Mesh HeatGear fabric, with all the benefits of UA Compression, delivers total ventilation Breathable ArmourVent mesh back panel is ultra-durable & delivers superior ventilation 4-way stretch fabrication allows greater mobility in any direction Moisture Transport System wicks sweat & dries fast