The warm baguses high-tech patented phase change energy storage materials as filling material, environmental PVC compound fabrics as packing. And it does not contain preservatives, each process have been inspected strict , so this products are safety and reliableness. It has a non toxic certificate with SGS and MSDS. The warm bag needs no power. the internal material is phase change energy storage material which can keep temperature constant for 6 to 8 hours. It can be used recycle 4 years. The temperature takes 40 centi-degree, which is appropriate for the body. It is convenient and economic for use for relieving cold, activating blood circulation etc. Temperature constant at40 degrees, suitable for human body temperature, the body not feel scalding in winter,it can be suitable for all parts of human body. Temperature constant at40 degrees,more than8 hours without electricity, economic and environmentally friendly. method of usage: 1.heating 3 minutes in microwave or boiled water soak a few minutes before use ,and it can keep constant temperature for 6 to 8 hours. 2.After the heat began to warm into a liquid, after the release of heat into a solid.3. Temperature drop and then continue to put the microwave oven heating or boiled water soak a few minutes.