RubberHe makes these Winter Boots as light as helium, 50% lighter than natural rubber, but as strong as iron. Plus, the 600-denier nylon uppers are waterproof. And an 8mm Thermal Guard liner keeps you warm on any frozen tundra down to -40AdegF. Waterproof 600-denier nylon uppers, rubber shell RubberHe outsole remains flexible in all temps while also offering top traction Removable 8mm Thermal Guard liner is also moisture-wicking Adjustable snow collar with bungee lace lock Hook-and-loop midfoot strap Get these Winter Boots and Go Pack Snow!