This 18 quart, 110v/230v volt heater, high quality warmer was designed especially for heating massage stones, and is large enough for full body treatments or servicing more than one client at a time. It features a Teflon coated removable water reservoir with an easy-to-clean finish. The temperature control features a "preheat" setting of 375 degrees to heat the water quickly as well as providing an "operating range" of 120-150 degrees that lets you rapidly bring the stones up to the proper temperature for therapeutic use, and then maintains a constant, even temperature.