Holley HP Billet EFI By Pass Fuel Pressure Regulator. Two Port Adjustable from 15 to 65 PSI. 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. They feature a black bright dip anodized body and a clear bright dip anodized top for corrosion resistance and good looks. The Holley 12-846 fuel pressure regulator features(1) -8 AN O-ring inlet, (1) -8 AN O-ring outlet, (1) -6 AN O-ring return. Adjustable from 15-65 psi for precise fuel pressure adjustments. Constructed of billet aluminum with a black anodized base and clear anodize top for good looks. Used in systems with a return line back to tank. Includes fitting for manifold reference. Use with electric pumps only. (1) -8 an o-ring inlet, (1) -8 an o-ring outlet, (1) -6 an o-ring return. 1/8 NPT gauge port. Designed for use with the Holley® HPT in-line fuel pumps or other high pressure electric pumps where return line is needed. Gasoline / Diesel / E85.