The foot warmer patch contains iron powder and activated carbon. It can generate heat to provide sufficient warmth for the bottom of your feet or body; it's very helpful for women with menstrual cramps, back pain, and cold hands and feet. Its usage is simple: peel off the non-woven fabric sticker; stick the patch on the outside, put on socks, and enjoy the warmth of your feet for 6-8 hours. Easy to use and can be used for outdoor sports, providing you with warmth during the cold season.