Holley Billet Fuel Pressure Regulators Are Part Of A Complete Line Of Fuel System Products From Holley. They Are Precision Machined From 6061-T6 Billet Aluminum For Strength And Durability. These Regulators Are Adjustable From 4-65 Psi And Will Handle Both Carbureted And Efi Applications. They Are Offered With Two Port Sizes, 3/8" Npt Or 6An To Adapt To Your New Or Existing Fuel Lines. So, If You Are Currently Running A Carbureted System But Plan To Upgrade To Efi In The Future, These Regulators Will Have You Covered Either Way.