Getting the most out of your performance parts comes down to the details. When faced with hard driving conditions, a vehicle's cooling system becomes highly pressurized. Stock caps are not equipped to handle higher pressure, causing fluid to leak out into the overflow reservoir. The Mishimoto High-Pressure 1.3 Bar Radiator Cap is rated at a higher pressure and will keep coolant where it needs to beľ flowing within the system. Rated at 1.3 Bar (19lbs) pressure. Fits most domestic vehicles.