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