Under Armour HeatGear Flyweight Run T-Shirt - Men'sThe Under Armour HeatGear Flyweight Running T-Shirt features an ultra-lightweight, smooth fabric that provides extreme comfort and performance without adding weight. The blown-out mesh back and underarm panels provide superior breathability where you need it most. This running t-shirt also features anti-odor technology and a reflective logo that boosts visibility and safety during low-light runs. HeatGear® is best for weather between 75 and 100 degrees. 100% polyester. Imported.