The Keen Summit County III Boot is built to handle Summit County winters, and those are pretty harsh winters just ask any Coloradan. Or Coloradoan. Or Coloradanese. Anyway, the Summit County III surrounds your foot in insulation from under your foot to just above your ankle. Keen uses its 400 gram Keen. Warm insulation, which is made with charcoal to hold heat in an eco friendly cradle of foot toastiness. Between the sole and footbed, Keen places a Thermal Heat Shield to keep the cold snow from giving you the chills. Keen's Shellback Heel Support cradles your heel for added support and reduced slippage. The tough nubuck upper with its Keen. Dry waterproof breathable membrane is built to hold up to winter after winter of abuse, and the Keen. DCR outsole is designed to harden in cold temperatures for better traction on slick, icy surfaces.