Under Armour Tech HeatGear Short Sleeve Running T-Shirt Polyester Lightweight UA Tech Fabric - A softer, more natural feel for superior comfort. 4-way Stretch Fabrication - Improves mobility, while helping to maintain shape. Signature Moisture Transport System - Wicks sweat away from the body, keeping you cooler and drier. Regular Fit - A slimmer athletic cut that delivers better mobility by eliminating the bulk of extra fabric. Heatgear - For when it's hot. Keeping athletes cool and dry. Lightweight, high-performance fabric maximizes comfort and breathability.