This version of Sorel's Caribou features a wool inner boot to keep feet warm, dry, and cozy during activities in winter weather, along with a full grain leather upper, waterproof construction, and slip resistant traction.. . . . Sorel comfort rated to 40AdegFC for extreme warmth. Removable, insulating 9 mm wool inner boot:. Wool manages moisture and regulates temperature for exceptional warmth. Reinforced seams and heel area for exceptional durability. Stretch front shaft ensures comfortable fit and seals cold air out. Sherpa Pile snow cuff to keep snow out. Aero Trac rubber outsole and nonloading lugs for sure footed, slip resistant traction on snow and ice. 2.5 mm bonded felt frost plug midsole increases thermal barrier between your feet and cold ground. Seam sealed waterproof construction to keep feet dry. Waterproof full grain leather upper for protection and durability. Handcrafted, waterproof, vulcanized rubber shell to keep feet dry. Shaft height: 10 in. 25.4 cm. Calf circumference: 17 in..