Flex the metal coin inside the salt-based solution to activate a chemical reaction. The liquid turns to crystals and the energy created from the conversion heats the pad to 54 celsius in approximately 30 seconds (and will stay warm for 30-60 minutes depending on ambient temperature). Bring to any mobile treatment and instantly heat them up for use. After first use it can be re-heated in hot water (leave until the crystals dissolve) or microwave. Can also be used as a cold compress by placing in the fridge (DO NOT FREEZE).