Adapting to the world of max-cushioning running shoes, the Altra Duo takes plush underfoot midsole cushioning and marries it with their uniquely-shaped footbed. The Foot-Shape™ toe box gives runners plenty of room for their toes to splay, naturally. Though designed to feel fast and light, this shoe certainly doesnt skimp on the cushioning with one of the thicker and softer midsoles from their shoe line-up. Lovers of the zero-drop aspect of Altra still achieve that same feeling throughout each wear. Upper:Lightweight and flexible engineered mesh upper offers breathability. Lace-up front offers an adjustable fit. Midsole:The Zero Drop™ platform with a FootShape™ toe box allows the toes to relax and spread out naturally and the big toe to remain in a straight position for more stability and powerful toe-off to maximize running performance. Outsole:Full rubber outsole promotes durability and traction. Foot Pod Outsole technology maps the bones and tendons of the foot to let it flex where it naturally wants.