Holley fuel pressure regulators are designed to precisely control the fuel pressure from the fuel pump to the carburetor. Too much fuel pressure for a given needle and seat assembly can overload the needle and seat and may cause flooding or drivability problems. Each Holley fuel pressure regulator is fully adjustable so regulating the fuel pressure to your engines needs is a simple task. All Holley regulators are pre-set at the factory so there is no guesswork when first installing the regulator. Adjustable fuel regulation from 4-1/2 to 9 psi. Aluminum billet body and top casting cover are hard coat anodized for corrosion resistance. Three fuel pressure gauge mounting options (fuel pressure gauge included). Compatible for use with gasoline and methanol/alcohol.