STRETCHWEB WITH CONTINENTAL: rubber outsole with superior grip that adapts to every runners foot strike by moving in harmony with boost to provide a smoother and more flexible ride. PRIMEKNIT: new knit provides enhanced breathability and ventilation around key sweat zones under the cage and in the forefoot. FIT COUNTER: supportive heel construction designed to enable the free motion of the achilies tendon BOOST: temperature-independent cushioning provides maximum comfort and energy return in all climates.