Under Armour Women's SpeedForm Apollo Running Shoe Synthetic-and-mesh Nylon/Synthetic Upper - Allows air to fully permeate the shoe's interior, encouraging an environment that is cooler, drier and altogether more pleasant. Ultrasonic Welded Construction - Utilises a network of Bemis Tape seams to deliver a shoe that is incredibly robust and resilient. Silicone Heel Grip/External Heel Counter - Work in concert - the former from the inside and the latter from the outside - to ultimately grab the heel and secure it firmly in place for an improved, chafe-free fit. 4D Foam Sockliner - Wicks moisture away from the skin, delivering seamless comfort and a dry, blister-free environment. Micro G Midsole Compound - Cushions the foot and attenuates shockwaves superbly.