This heat pack is a personal favorite of HotShotz. It is small enough to travel, yet is still big enough to feel the heat and actually enjoy it. Works well for pretty much any part of your body. Great for cramps, sore, achy muscles and joints. Also, keeps you warm, whether at home or on the go at football games or out and about or camping. Also, great for using if you suffer from coldness from Raynaud’s, anemia, thyroid problems, or iron deficiency. It is the longest lasting heat pack that HotShotz makes. To use the HotShotz Portable Round Warmer, squeeze the activator button until it clicks and the warmer will automatically heat up on its own and be ready to be used. To recharge after first and each use thereafter, wrap with a fabric cloth (dish cloth, for example), place and leave the heat pack in a pot of boiling water for 10 to 20 minutes, making sure all crystals have melted. Take it out of the pot and let the warmer cool down to room temperature and it’s ready to be used! Usability will generally last an hour. Time will change depending on how you use it and how well you insulate it.