The 3.7-volt Premium Bluetooth® battery is exclusive to our Premium BT heated sock and can be controlled with the MW Connect® App. To learn more about which garments are compatible with what batteries, check out our Mobile Warming® Technology Battery Compatibility Chart . Specifications: ONE BATTERY INCLUDED Rating: 3.7volts, 2200mAh Input: DC Jack 4.7volt@1A / Micro USB 5V@0.8A Charge Time: 5-6 hours Size Inches: 2.8in x 1.8in x .5in Size Metric: 73mm x 47mm x 13.5mm Garments Compatible: Premium BT Socks Premium Pink BT Socks