The Hot 'n' Cold Pak from Lifoam is made with a special poly bag and gel that allows this item to be heated or frozen. You can use it to keep hot things hot and cold things cold.A must have accessory for your insulated food pan carriers, this hot or cold pack is convenient and easy to use. This reusable pack can be frozen and used to maintain temperatures of cold foods -- or heat it in the microwave to help hot foods stay hot! This versatile pack is just what you need when traveling with food to a different location or creating a comprehensive first aid kit.