The Therm-ic Ultra Heat Boost Mittens Women provides the ultimate warmth & protection from the elements, suited for those who really struggle with cold hands while skiing. As mittens keep your fingers together, they help improve heat retention & circulation. Lightweight lithium batteries warm the internal elements which wrap 360 degrees around the fingers providing up to 10 hours of heat. There are three different temperature settings, & the batteries are contained in a zipped compartment to extend the time at which they last. To charge simply attach them to a USB (Universal Serial Bus) plug. The glove itself uses Primaloft Gold insulation, a leather palm & a 10k waterproof/breathable membrane. To extend the life of the batteries as much as possible, Therm-ic recommends storing them in a cool place (5°C to 20°C) after they have been half charged. During storage, the batteries should not be connected to the glove or the USB (Universal Serial Bus) charger.