This adapter threads into an AN8 male O-ring port and presents an AN12 male 37-degree flare for the hose. It is used where the plumbing run is AN12 but the component it terminates at is only tapped AN8, which is common when an oil or fuel system is upgraded to larger hose ahead of the hardware. Flow is limited by the AN8 port, so choose it for hose continuity and routing rather than expecting a gain in capacity. The port seals on its O-ring against the boss face, so it goes in dry and needs only enough tightening to compress the seal squarely.