The full-grain leather and synthetic upper is seam sealed for a completely waterproof construction, and lined with 400g Thinsulate™ Ultra for high-warmth, low weight insulation good to -40° below zero. A built in gaiter locks out snow, while an Achilles adjustment strap with shatter resistant YKK Shokonlock™ buckle closure ensures a solid fit, fast. And with its molded waterproof thermal rubber shell and high-traction lugged outsole, it sets the benchmark for toughness in winter weather.