Warmawear Battery Heated Socks with Dual Fuel Pocket Dual Fuel Technology allows you to have back up heat, extend the heating life of your socks and maximise the sock warmth by combining our disposable heat packs with the battery heating Advanced carbon ceramic infrared heating element distributes heat gently and evenly Socks stay warm for up to 5 hours, and require 6x AA batteries each Discreet battery boxes with adjustable leg straps and flexible cables can be positioned over ski boots or wellies Convenient on/off switch located on battery box - no need to remove the batteries to switch it on or off