Electrothermal hot water bag, doesn't need to be refilled every now and then - already filled with water, galvanothermal energy conversion agent that keeps water warm for 2 to 8 long hours, plug the device in a 220V socket and let it sit for 8 to 15 minutes or until the red light turns off automatically, automatic temperature control, made of high-quality plastic film and complex fiber for a leak-free factor, internal pressure-protection device which restrains air expansion thus preventing accidenta.