Keeping you Ready for the Road Ahead , the Gates 33579 Heavy Duty Thermostat has an OE-exact design, fitting applications with 3/4” deep filler necks. Gain consistent valve response for smooth performance and accurate engine cooling with the temperature sensitive heat motor of this heavy duty engine coolant thermostat by Gates. Experience accurate opening and closing, regardless of pressure changes, with the quality controlled factory calibration of this heavy duty thermostat. FleetPride is your First Click in Heavy Duty .