HOLLEY 12-879 Return Style Fuel Pressure Regulator 3/8 NPT Boost Reference – 1:1. 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. A second pressure spring is included allowing you to increase the fuel pressure range up to 65 psi for EFI systems. 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. Adjustable from 4-65 psi for precise fuel pressure adjustments. Constructed of billet aluminum with a black anodized base and a clear anodized top for good looks. Used in systems with a return line back to the tank. (1) 3/8″ NPT Inlet; (1) 3/8″ NPT Outlet; and (1) 3/8 NPT Return Port. Includes fitting for manifold reference. Includes an 1/8 NPT gauge port. Boost Reference – 1:1. The 4-15 psi carbureted spring comes installed in the regulator. Compatible with Today’s Complex Fuels. CCS Kits are supplied with the highest quality components that meet or exceed original equipment specifications and all CCS kits are compatible with today’s complex fuel. Carburetor Collectible Specialty Thanks You for Your Support! Please before leaving Feedback. We strive for perfection, and welcome the opportunity to correct any issues with your order. Your satisfaction is our #1 importance. You will receive a response within 48 hours. Please limit your questions to the products we sell.