DescriptionEXPERIENCE ULTIMATE ENERGY RETURN WITH ULTRABOOST 21.Prototype after prototype. Innovation after innovation. Testing after testing. Meet us in the hot pursuit of the pinnacle harmonization of weight, cushioning, and responsiveness. Ultraboost 21. Say hello to incredible energy return.DetailsSock-like fitLace closureadidas Primeknit upperTextile liningSupportive heel counterBoost midsoleWeight: 10.9 ounces (size 9)Midsole drop: 10 mm (heel 30.5 mm / forefoot 20.5 mm)Stretchweb outsole with Continental RubberPrimeblueProduct color: Core Black / Core Black / Grey FiveProduct code: GX5236