An AN8 to 3/8 female quick connect adapter. Choosing AN8 over AN6 is usually about flow: a bigger pump or a high-output engine will drop pressure through a smaller line, so the aftermarket side of the system runs AN8 while the vehicle side keeps its 3/8 quick connect. This adapter joins the two without cutting the factory line. Bear in mind that a size step is only worthwhile if the rest of the run is sized to match, and that the factory 3/8 section becomes the limiting point in the circuit. Verify the coupling latches fully and check for leaks at first pressurisation.