NU Technology Warm Stone Pocket Heater with Negative Ions and 3600 mAh Portable Power Bank for Mobile Devices (Sliver/Purple) double-sided pocket heater with two preset temperature control modes on 42 (107.6) or 47 (116.6) to ensure the most comfortable warmth it is also a 3600mAh USB Power Bank that can charge and power portable devices like iPhone, iPads and Android phones NU Warm stone double can also generate negative ion for your body health