Product details About this item Sole material Rubber Shaft height Ankle Shaft circumference 4 Inches Outer material Leather About this item Waterproof membrane seals out water and lets moisture escape Waterproof full grain leather and wool upper with a bungee lace with toggle for secure fit Bellows tongue keeps out debris and protective shell keeps feet dry 200 grams Primaloft Gold Eco Series synthetic insulation Vibram Icetrek outsole designed to provide the improved grip on very cold, icy, or snowy surfaces Description With 25 years of Merrell's women's-specific fit, the Siren 4 Thermo is uniquely engineered to cradle the distinct contours of female feet, providing comfort, support, and stability even on the longest hikes with added insulation for warmth and protection.