Keeping you ready for the Road Ahead , the Gates 33578 Heavy Duty Thermostat has an OE-exact design and fits applications with 3/4” deep filler necks. Experience accurate opening and closing, regardless of pressure changes, with the quality controlled factory calibration. 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. FleetPride is your First Click in Heavy Duty .