DryGuy Green Heat Rechargeable 4400 mAh Hand Warmer and Device Charger, Silver Temperature Setting: Low 107 Degree F & High 118 Degree F Multifunctional design also works as portable mobile phone charger Standard use time: 4-5 hours Power Supply: Rechargeable (micro USB 5V/4400 mAh max input) Over Charge, Over Discharge, and Short Circuit Protections