polyester Heating Pads system compatible with any 5V/2A USB power supply from cellphone Charger, Cellphone Power bank , Car jump starter, Car phone charger, and others. 5 heating pads can heat shoulder, back, hip and feet areas when put it into Sleeping bag. (Battery not included.) Extra heat from electronic heated pads can warm your body at chilly midnight when you are camping outdoor. If you feel hot, just simply lower the heating mode or turn it off. Do not need to prepare an expensive down sleeping bag which sometime too hot for summer. 198X61CM (6.5X3FT) fit with most of Adult sleeping bag. And the weight only 2 pounds, with compact carry bag it is easy to be packed and carried Water proof Oxford shell and Soft flannel lining keep you warm and comfy. Heated sleeping bag liner can also be used as Sofa seat cushion, heated blanket, Heated car seat cushion etc.