HFS may be short for Happy Feet Shoes, Hyper Flexible Soles, or, more likely, what you will exclaim when you try this 7.0 ounce (M9) true road runner, Holy ___ ___! Your feet will love the natural comfort of the wide toe box and zero-drop design. The tire-inspired tread keeps you sure-footed. The 37.5 sockliner and breathable engineered mesh keep you cool. Hidden instep and mid-foot tensioners give you the security you need to go for that new personal best Light, Grippier, and ComfierLike the original HFS, the HFS II is super lightweight (8.3 oz, M9) so you’ll feel like you’re flying down the road. And with a new tire tread-inspired outsole, you’ll feel secure even if you go off road.