Useful. Li Cheng's hot compress bag is a product invented by Li Cheng, which contains iron filings, activated carbon and other substances. It has the effects of promoting blood circulation, removing blood stasis, relieving swelling and pain, warming channels and dispelling cold, and dredging channels and collaterals, which is helpful to relieve pain and is useful. When using the hot compress bag, it is best to stick it directly on the skin through clothes, which is difficult to control the temperature and easy to burn.