The product has been filled with galvanothermy energy conversion agent, which helps it to warm up quickly and keep warm for a long time. commonly, after charging for 7-12 minutes, it can be used for 2-10 hours, which is 2 hours for hand warming or 10 hours for quilt warming. it has automatic temperature control to avoid being over heated. Starts heating when the light starts shinning and stops when the light extinguishes. This product is explosion and leakage proof. Protection device installed inside can restrain the air expansion while the vinyl film and high strength complex fiber guarantee no leakage of the product.