This "Smart Heater" was used in Sundance Spas from 2000 to present. This heater includes the internal high-limit thermo disc switch and wiring. Smart Heater Description: Therm Products Replacement 240 Volts Titanium Heater Element 3/4" Barbed Fittings For Plumbing Note: Sundance Smart Heaters manufactured from 01/01/2000 thru 06/12/2000 utilized a small circuit board inside the heater. Since 06/12/2000 this board is no longer needed. Replacement heater will replace this version.