Buddy Club Racing Spec Radiator Cap is a direct replacement for the stock radiator cap and improves cooling performance. A radiator cap functions to increase the pressure inside the radiator so that even if the water temperature exceeds 100C, boiling will be avoided. Stock OEM radiator caps are rated at 1.1 BAR. The Buddy Club Racing Spec Radiator Cap increases the pressure to 1.3 BAR, thereby improving cooling performance *** Note *** Radiator cap will not work with stock S2000 Radiator.