HotSpring Spa '06-current Multi Thermostat. This Control Thermostat Thermistor communicates the actual water temperature to the controller to shut off the heater when the spa reaches target temperature. It is used on all 2006-current Hot Spring Hot Spot Mallorca, Hot Spring Hot Spot Sorrento, Hot Spring Hot Spot Trinidad & Hot Spring Hot Spot Tobago spa models. It is also used on all 2006-current Hot Spring Solana RX, Hot Spring SX & Hot Spring TX spa models. Used on the 2009 forward Hot Spring.