To be honest, I bought this, too. It is the so-called infrared hot post, which is covered with dots. When in use, it is fixed on the belt and close to the back, and then fixed firmly with the belt. It is true that after using it for a period of time, I feel that the infrared sticker on my back has a feeling of fever, but after taking it off, there is no fever, only my body temperature makes it hot. After many experiments, I found that the feeling of heat is not real heat, but small pain points pressing on the skin, which seem to be burning. The tighter the belt is fixed, the faster the heat will come. Personally, I think infrared heating is a gimmick, and the real thing is the illusion of pain.

Please accept it, hehe, this is the result of my careful experiments, and I have accumulated some physical knowledge and a little understanding of infrared rays.