MOBILE WARMING WOMEN'S CLASSIC SOFTSHELL VEST (MEDIUM) (BLACK) The Windshark 4-way stretch high breathable, waterproof fabric provides additional flexibility needed in active outdoor sports. Designed to be used for layering or worn on it's own. Features three heating panels lined with steel alloy fiber elements. Optimum placement with two panels on the chest and one on the back provide quick warm-up and even distribution of heat where you need it most. Includes one 7.4V 2.2Ah rechargeable lithium-ion battery and charger.