2Pcs 2200mAh batteries with two USB cables, mobile power supply for electric heating socks, 3-gear adjustment with indicator lamp, USB rechargeable, convenient to use. Features: Using mobile USB charging, easy to use, safe to operate, 3.7V low voltage, far below the human body's safe voltage of 36V. 3-gear adjustment, adjust different temperatures according to needs. Connect the battery to the power cable, press the button on the battery to start heating. USB interface, convenient to charge, mobile power, power bank, phone charging head, car charger all can use. The battery can be put into hidden battery pocket of electric heating socks. Specifications: Material: Plastic Color: Gray socks with hidden heating sheet, Black socks with hidden heating sheet, 2200mAh batteries (optional) Heating Temperature: 40,45,50 Power Voltage: 3.7V Heating Material: Composite fiber heating sheet Gear Adjustment: 3-gear hot compress Care Site: Feet Package Weight: 100g / 3.53ounces Package Size: 195 * 100 * 72mm / 7.68 * 3.94 * 2.83in Note: Remember to remove the battery before washing. W21860-2: Package list: 1 * Pair of Electric Heating Socks