Serious boot for rugged terrain The new 10" Mountain Extreme 400 is made from one piece of 2.8mm top grain leather on a durable nylon midsole and features a high-traction K Talon outsole. Waterproof, breathable Windtex membrane and 400g Thinsulate insulation keep you warm and dry. Thanks to its great support, it is sure to be your favorite boot. Really you will be amazed at how lightweight and comfortable. 4 lbs.