Designed to be used in systems with a return line back to tank, It is adjustable from 4.5-9 psi for precise fuel pressure adjustments, Comparable and interchangeable with popular Holley® 12-803BP regulator, Features one 3/8" NPT inlet, one 3/8" NPT outlet and one 3/8" NPT return (or bypass), Constructed of billet aluminum with a black anodized base and clear anodize top for good looks.