Penguin Hand Warmers is made of ABS material build in 3000 mAh lithium rechargeable battery. Press the switch and instantly release the warmth for you. Rapidly warm up double sides in seconds. 2 levels of temperatures 45°C/55°C at your choice. It can also be used as a power bank to charge your electronic device at any time. The hand warmers are very suitable for winter night fishing, hunting, golf, skiing, backpacking, hiking, winter camping, outdoor activities etc.