ReDo Reusable Hand Wamer 2 Pack, Emergency Zone Brand
Perfect to slip into your pocket to keep your hands warm on those cold winter days or keep in your emergency kit just in case.  Flexing a catalyst disc in the warmer causes the liquid in the pouch to crystalize, generating heat.  To recharge, simply place in boiling water to melt the crystals back into a stable liquid.  Directions are printed right on the warmer.