797 Performance Coolant Restrictor Kit All 5.7, 6.1, 6.2, 6.4, Gen 3 Hemi's Including Hellcat Restricting coolant flow leaving the engine lets you control the amount of heat absorbed by the coolant.  Simply removing a thermostat can causes the hot coolant to move so fast and the radiator does not have enough time to allow for adequate cooling, and does not allow for proper warm-ups. 6061-T6 Aluminum restrictor plates are mounted under the water outlet and sealed with an OEM-style gasket. Integrated Air Bleed hole to allow trapped air to be released.  (must be installed in the 12 o'clock position) Kit consists of three restrictor plates, 5/8", 3/4" &1" ID Bores, and one gasket. It's recommended to start with the middle bore and change to the next size or down up if needed.  The middle size runs most vehicles 180-190F with working heat but ambient temperature, humidity and air density affect thermal absorption.  All sizes are provided so you can adjust until you find what works best for your situation. THE EXTRA GASKET OPTION - Is available so that in the event you want to switch sizes you can do so quickly without transferring the gasket over Just like a 180 or 160 thermostat, tuning will be required to adjust fan temps and rationality warnings. We advise setting fans as you would for a 180 thermostat. Always start with the middle disc and change up or down a size as needed.  We do not provide tune settings. This product is for off-road / racing use only where stuck thermostats that plague the aftermarket cannot be accepted.