The first Toe Cap® heat sock with merino wool and compression. This is a sock with integrated heating element under and over the toe section, powered by rechargeable batteries attached with snap fasteners at the top of the shaft. Batteries are sold separately. The Lenz battery pack can be used to adjust the heat both manually and via Bluetooth in a mobile phone app. The mobile function is super practical as you do not need to pull up the trousers and adjust the sock when you are in the ski lift. Remember to always start the socks before leaving home; to warm up feet and shoes that are already cold user considerably more battery power and takes much longer than just maintaining heat. The battery life naturally also varies depending on the outside temperature.