 This heat product is a cloth wrap that houses several small disks made of iron powder, activated charcoal, sodium chloride, and water.When the wrap is removed from its sealed pouch and exposed to oxygen, the disks oxidize, producing an exothermic reaction.When this product was applied to the low back muscles, it provided greater pain relief for 24 hours after application when compared to ibuprofen, acetaminophen, and no treatment.