Under Armour Heatgear Flyweight Running T-Shirt - Women's The Under Armour HeatGear Flyweight Running T-Shirt features a super-soft, anti-microbial, feather-light fabric that provides a faster, lighter, and cooler performance. This high-tech running shirt also features UPF 50+ that protects your skin from sun damage. The stretch mesh back panel increases ventilation and breathability, while a dropped-back hem provides extra coverage. Thanks to the 360 degree reflectivity, your safety and visibility are increased. HeatGearŪ is best for weather between 75 and 100 degrees. Semi-fitted fit. 100% polyester. Imported.