Now in its third iteration, the Constrictor Boa is considered one of the best winter boots available on the market. Designed to keep your feet warm and dry on snowy walks or after a day on the slopes, they are fully waterproof and feature Primaloft synthetic lining. A Primaloft Aerogel insole- originally developed for the NASA- provides insulation from below, even when compressed to shield you from the ground temperature. Viking\'s proprietary Grip Concept® outsole delivers durability and traction, even on slippery surfaces. A BOA® closure system lets you adjust the fit easily, even when wearing gloves, and reflective details ensure you remain visible in dark conditions. Viking. Details: With Boa Closure System. Obermaterial: Textil, Synthetic. Oberes Futter: Primaloft Innenfutter. Innensohle: Primaloft Aerogel. Mittelsohle: Eva. Außensohle: Gummi. Wasserfest.