éWeight: 9.8 ounces (size 9); Runner type: natural; Stack height: 29 mm / 19 mm (10 mm differential) boost 's energy-returning properties keep every step charged with an endless supply of light, fast energy adidas Primeknit is carefully engineered to naturally expand with your foot while you run to give you a more comfortable fit and help reduce irritation Molded eyestay as part of dynamic fit system that hugs your foot like a second skin Lightweight cushioning midsole; Molded heel cap; EVA outsole for smooth rideé