Reusable hand warmers for instant warmth on a cold winter day. These hand warmers are easy to activate, you simply activate them by pressing the metal piece that appears on the bag. Once the bag begins to crystallize, they will release heat, and can stay warm for up to 90 minutes at a time. You can advantageously use them in your jacket pocket or in your gloves on a cold winter day. The bags are reusable as you just have to boil them in water, then let them cool completely.