Waterproof, full grain leather upper. 9mm removable, ThermoPlus felt InnerBoot provides superb warmth, moisture transfer, comfort, and durability. Acrylic/wool blend snow cuff. 2.5mm bonded felt frost plug in the shell to provide an extra layer of insulation and warmth. The frost plug is a 2.5 mm piece of EVA that is in the heel and forefoot. Handcrafted, waterproof vulcanized rubber shell with lug outsole. Aerotrac outsole. Sorel Rated: -40F/-40C. Need a replacement liner? Click here or here. Water Shoes, Hiking Shoes, Boots.