Great for treating lionfish stings, heating a wetsuit, or just to keep your hands warm. The 3×5 is great as a hand warmer, in pockets, under beanies, and works great for spot treatment, arthritis, poor circulation and hot stone massage. The 3×5 lasts about an hour depending on how well you insulate it. You can also use the heat pack as a cold pack. Just place it in the freezer for up to one hour and it will stay soft and flexible.