The Muck Arctic Sport Waterproof Insulated Boots have CR flex Foam uppers with four way stretch nylon snag resistant covers. 100% waterproof and lightweight. The stretch fit top binding conforms to calf. Fleece lining, a molded midsole with removable footbed, premium steel shank arch support and vulcanized rubber soles. Double reinforced instep has 2mm thermal foam underlay for additional warmth.