Turtle Fur Lectra Sox Hiker Boot Socks, Electric Battery Heated Socks Other Size: XS/S fits Men's 5-8.5 & Women's 6-10 - Medium fits Men's 9-10.5 & Women's 10.5-12 - L/XL fits Men's 11+ Wool blend (17% Wool) heated socks provide 6-8 hours of warmth. Uses "D" cell batteries (not included). Battery pouch is attached to sock. Great for hunting, ice fishing, hiking, and sporting events. Won't shock, even when wet! Padded reinforced heel & toe, and recessed heating element help focus heat in the toe to keep your feet from getting cold. The Lectra Sox are designed to keep feet warm, but not hot. Engage the heat only after you begin to feel the cold. Maximum benefit will be obtained by turning the socks off and on often.