Our hand warmers contain iron powder and toner. It can start heating immediately, the heating time is extremely short, and you can feel the warmth very quickly. Its use method is very simple: 1. After opening the package, take out the patch and stick it on the inside of the clothes. 2. The patch will start to heat up in 15-30 minutes. 3. The insulation effect can reach 10 hours. It is suitable for use when you are cold. It releases heat through a chemical reaction, raising body temperature and warming hands. Suitable for winter activities, including outdoor outing, writing heating, relieving local hand pain, etc.