Ignik's Heated Sleeping Bag Liner can change the degree of your sleeping bag up as high as 20 degrees. It's electronically charged to provide that level of heat for one hour, or you can spread it out on a lower setting for up to eight hours. Ignik made the exterior out of soft, recycled polyester with a heat-trapping carbon layer fixed to a groundcloth that reflects heat back your way. This liner included a USB adapter that connects the liner to compatible 5V and 12V batteries for charging.