Under Armour Heatgear Sonic Bra - Women's The Under Armour HeatGearŪ Sonic Bra is made with a super-light fabric that delivers superior coverage without weighing you down. Signature Moisture-Transport System wicks sweat to keep you cool, dry, and light. Lightweight, four-way stretch construction improves mobility and accelerates dry time. Classic racerback design provides mobility and is great for layering. HeatGear works best in weather between 75 and 100 degrees. 84% polyester/16% spandex. Imported.