... rechargable wamer 3.portable wamer 4.USB wamer portable reusable usb electronic hand warmer detail description as follow: Product feature: 1,Product ... long duration, convenient charging, multiple functions, wide application4,Reusable, than the general hand warmer with whenever and wherever possible, use of the ... -40°C •Application environment:-10°C-40°C portable reusable usb electronic hand warmer