Comfortable & Soft A high-quality fabric covers the outer layer of the heating pack, while flexible and double-thick PVC sheets cover the inner layer. Convenient Use The hot water bottle will be filled with water by yourself only, it is non-toxins and chemicals added, you need to charge for heating the bottle, and you have no like a rubber bottle, the water needs to be changed every time Safety Charging With a built-in automatic safety shut-off function, the power will be shut off when water is at 167 degrees, also the LED indicators will show you whether the bag is heating or not, so it's safe enough for us.