... 2.Infrared ray heat transfer 3.Portable,energy-saving 4.Battery:1800mAH Hand Warmer Christmas Gift Features:1.Portable, fashion, small2 ... -58C, Charging time: 4hours, Use time: 2.5hours3.Buit-in lithium battery, large capacity: 1800mAH4.Infrared ray heat transfer, speed up metabolism5 ...