This Reusable Gel Heating Pad Hand Warmer is a magica, crystallization type item because it's activated by flexing the small metal disc to produce heat. When you're done, just immerse in very hot water until contents become fluid and then allow it to cool. It is FDA approved, reusable, customized fun packs provides soothing warmth. Do not heat directly in microwave. Imprint this with your company name or logo for a spectacular giveaway!