Hand warmers taken to the next level… these HotSnapZ Reuseable Hand Warmers & Heating Pads come in convenient sizes and last anywhere from 30 minutes to hours, and even more impressively, they can be reused over and over again. At the risk of sounding a little like a chem class, here’s how they work… clicking the internal metal disk in a pouch causes a simple reaction between the water and the sodium acetate salt (a safe food grade salt) contained within that in turn triggers a continuous release of heat that was stored earlier. It’s like a heat battery that you turn on when you need it. No electricity or anything else needed. Just science at work, but that’s not to say it’s not magical to watch. And it works!