These Ski Heat First socks are perfect for a long day&';s skiing. These comfy, soft and self-heating socks are the best things for your feet when skiing. They feature 2 terry reinforcements on the shin and the forefoot for maximum comfort all day long. There is a heating element under the forefoot to keep your toes and feet nice and warm.Features: The socks are sold with batteries S-PACK 700B offering up 8 hours of heat. Ski Heat First TECHNICAL CHARACTERISTICS Soft and comfortable Reinforcements: shins and forefoot Heating elements: gentle and constant heat to keep your feet warm MV: medium volume, comfortable socks Knee length S-PACK 700B technical specifications Controllable via Bluetooth on your smartphone Offering up to 8 hours of heat S-Pack batteries are compatible with all Sidas Powersocks Pack includes a USB charger to charge both batteries simultaneously