As the first boot built around the 'Sure Tread' deep cleated outsole, Stream II remains a trailblazer in the premium wellington category. The adjustable rear calf strap offers a clean and assured side profile. Upper: Rubber Lining & Sock: Neoprene Sole: Rubber. Waterproof rubber upper 3.5mm insulated, Neoprene lining, Adjustable rear calf fitting, Internal structured heel support, Rubber kicker.