Thombo LLC Rechargeable Hand Warmer and Battery Pack, USB Cell Phone Charger, Reusable, Double-Sided, Portable, Power Bank Function Contains a 3500mA high performance battery that supplies over 3.5 hours of continuous heating at a temperature that stays just above 115 degrees Fahrenheit. The hand warmer heats from both sides and is surrounded by a soft rubber surface that makes it easy to hold and helps the handwarmer to not be too hot to the touch. It can either be ran continuously or it has a mode where you can blow into the product to get it to heat for 5 minutes at a time. The blowing mode is good if you don't want to take thick gloves off to turn the product off and on. The LED lights up to indicate how much power is remaining: Blue 60-100%, Green 10-59%, Red less than 10% The hand warmer can be recharged wherever there is a usb power source. It can be plugged into your computer or to a usb outlet adapter which is included with most cell phones. It also doubles as a cell phone charger. The cords are included to charge most cell phones. Iphones can still be charged by plugging in the iphone cable into the provided usb adapter.