Designed to meet the demands of race day athletes, the F4 utilizes an integrated nylon fabric to provide compressed venting and moisture wicking in the most extreme conditions. Made with Sorbtek, the F4 channels moisture away from the foot, keeping it cool and dry. Anatomical left-right foot construction allows for a precise fit, while a unique cushioning system provided comfort in specific pressure areas. Achilles protection reduces blistering on the back of the foot, and a front tab protects against shoe friction.