Invensys Appliance Controls, Eaton Thermostat. 5/16 Inch Bulb x 18 Inches Long. Single Pole Rated At 25 Amps. Maximum Temperature Rating At 107°F. For Best Results, The Bulb Is Should Be Installed In A Dry Well Or The Heater Tube Groove At Or Immediately Before The Heater. This Is For Safety. If The Thermostat Is Out Of Calibration, Do Not Attempt To Adjust. Replace The Thermostat With A New One.