The main body of the hand warmer is made of ABS with silicon surface, which is perfect for the curve of the palm, comfortable to hold and easy to carry. Quickly preheat the double-sided in a few seconds, the temperature is intelligently adjusted between 119 F and 126 F, providing a warming temperature of 4.5 hours or more. Press the power button to turn it on or off. ( We suggest children under 8 years old need to use it under the supervision of a guardian) .