Lenz 4.0 knee-high socks with small, latest generation integrated heating element. They keep your feet warm even trough the toughest winter. The socks are ergonomic and they have ring bandages for optimum support on the foot. Two special batteries power the heating element (for this product batteries are not included), which are attached to the socks by studs. Machine washable at 30 degrees. Material: 54 % polyester, 29 % nylon, 7 % merino wool, 5 % polypropylene, 5 % spandex. Breathing material, moisture management, pleasant to the skin. Suits for all 4 seasons.