Rechargeable Foot WarmerIt can generate heat compared to ordinary boots. The heated shoe comes with two 4000mAh rechargeable batteries. It uses carbon fiber electric heating wire and far-infrared heating method to quickly heat up within 10 seconds, covering the entire sole and toes. Your feet will no longer be cold and stiff in the cold winter. 2-Level Temperature ControllerThe heated socks have a 2-level setting heat controller, you can easily adjust the comfortable temperature. Long press the switch (2~3 seconds) to turn on/off, short press the button to switch temperature settings. Including high heat (109.4-112F, 3-4H, red light on), medium heat (95-107.6F, 5-6H, white light on). Automatically shut off after 3 hours Rechargeable heated slippers will automatically shut down after 3 hours by default. Equipped with NTC temperature monitoring and overheating protection chips, you can use it with peace of mind and don't have to worry about the toe warmer scalding your feet at low temperatures. Ensure your safety. Soft and High-Quality MaterialThe heated boots are made of faux suede and Berber wool, which are soft, skin-friendly, water-absorbent and breathable. Anti-slip pads are added to the soles of the socks to allow you to walk freely indoors. Ideal Gift for WinterPackage includes: 1 pair of heated slippers, 2 rechargeable batteries, 1 USB charging cable, 1 user manual. Thermal slippers keep you warm and comfortable all day, and the electric battery powered thermal socks make a great birthday/Christmas/New Year surprise gift for parents, loved ones and friends! NOTE: Heated slippers only come in one size and can be worn up to a size 9.