Viking Constrictor III WP Boot. Constrictor III delivers durable waterproof construction that keeps your feet warm and protected on subzero adventures. These high-performance boots feature a sturdy, water-resistant Primaloft lining and Primaloft Aerogel insoles that insulate feet from below. The Boa® Fit System lets you fine-tune your fit with the twist of a dial! Viking's Ultimate Grip Concept® sole delivers unbeatable traction on slippery surfaces. Reflective details illuminate for 360º of added nighttime visibility.