Disposable hand warmer with iron powder inside : it is disposable hand warmer which not be reused.The outside is nonwoven fabric, and inside it is some iron powder,salt,activated carbon,water etc.It will warm up over 5-10minutes later after opening the outer polybag. This kind of hot packs (hand warmer) can be put into your cloth pockets,gloves,shoes to warm fingers,hands or feet.