With a host of cold- and slush-busting features, KEEN Revel IV Polar Boots are built smart and built tough. Heat-holding KEEN.WARM insulation keeps feet toasty down to a teeth-rattling -25F and the KEEN.DRY waterproof/breathable membrane blocks out moisture while letting vapor escape, so your feet won't feel like they're trapped in a sauna. The Thermal Heat Shield footbed keeps cold out and heat in thanks to an outer layer of woolly softness, a middle layer of support cushioning and a thermal foil barrier to harness radiant heat. And true to KEEN form, they offer superior cushioning, ankle support and stability, plus plenty of room for your toes to spread out. Last but not least, the leather is sourced from a Leather Working Group-certified tannery, so you can feel good about treading more lightly on the environment, too.