Quality controlled factory calibration assures accurate heat control under extreme variations in temperature, load and engine vibrations. Approved for marine applications.Heavy-gauge brass and stainless steel with positive piston heat motor.Available in Choke type, Top By-Pass, Bottom By-Pass, Side By-Pass, Normally Open and other types to meet heavy-duty cooling system designs.Note: Seal should always be changed when new thermostat is installed.Gates – Driven By Possibility