Foot warming bag electric usb feet warmer pocket size: 30x30cm 1. made of high-quality flannel composite fabric, it is light, soft and comfortable, with good thermal insulation and long service life. 2. as a necessary warming artifact in winter, it heats at a constant temperature (50-60°c) to bring comfortable warmth to your feet in cold weather and drive away the cold. 3. universal usb interface, compatible with a variety of charging devices, such as adapters, mobile power supplies, car usb interfaces, computers, etc. 4. the portable foot-warming bag is easy to operate, and can be used by connecting usb interface, without charging or self-provided batteries, which is more environment-friendly. warm slippers feet warm slippers heating glove usb electric heating pad winter hand foot warmer washable household foot warmer.