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Winter warmth doesn't get any more comfortable than this slip-on bootie that's insulated with ThermoBall™ technology to achieve the warmth equivalent of 600-fill down while providing the wet-weather insulating performance of a synthetic. Tighten the barrel-lock drawcord on the faux-fur detailed collar to trap hot air and stay warmer while padding around Everest Base Camp or on winter walks.
Developed in partnership with Primaoft, Inc., ThermoBall is a revolution in insulation technology. Unlike traditional continuous-filament synthetic insulation, the small, round PrimaLoft synthetic-fiber clusters closely mimic down clusters, trapping heat within small air pockets to retain warmth. Independent clo testing by Kansas State University has shown that ThermoBall has warmth equivalent to 600 fill goose down. As a result, ThermoBall can offer the lightweight warmth and compressibility of down with the wet-weather insulating performance of synthetic insulation.