Synthetic soleSHOE SIZE: D = Medium widthENERGIZED FEEL: Delivers a responsive and springy ride to add extra lift to your stride without compromising support or speed.SUPPORT SYSTEM: Next-generation Guide Rails provide holistic support by guiding your feet into alignment??reducing heel and shin rotation, and keeping excess knee motion in check.RESPONSIVE CUSHIONING: This responsive cushioning provides best-in-class energy return, for a dynamic, springy, responsive ride. Your own energy is conserved, allowing you put more into every stride.SECURE FIT, INCOGNITO COMFORT: The dynamic midfoot wrap makes feet feel secure inside of the highly adaptable Fit Knit upper. The covert wraparound heel collar treats your feet to plush comfort. A sueded heel tab protects your Achilles from irritation.