A Heat Factory Warmer is a soft, lightweight pouch which begins to activate and generate its own heat when exposed to the air. They can be used any time you need instant warmth and are especially great for skiers, hunters, winter sportsmen, kids and emergencies. Heat Factory Hand Warmers are a terrific way to stay warm! Hand Warmer Package large size warmers are designed to be used in pockets, or gloves. Heat Factory Hand Warmers provide from 8 to 24 hours of continuous warmth, depending on the size. Keep some in your backpack, pocket and purse.