FuelCell midsole delivers a propulsive feel to help drive you forward; Even more foam underfoot than its predecessor; Redesigned outsole with more rubber at the forefoot; A redesigned heel and tongue bring added comfort for fast miles; 227 grams (8 oz); PEBA/EVA foam blend provides durable, lightweight cushioning and fast underfoot feel; An engineered mesh upper provides lightweight support and breathability; FantomFit upper offers ultra-light bonded support