This AN920-series adapter puts an AN6 male 37-degree flare on the hose side while threading into an AN4 O-ring port. It solves the common problem of a component with a small tapped boss that still needs to feed a larger circuit, such as running an AN6 fuel or oil line off a casting only drilled for AN4. Bear in mind the port itself is the restriction, so use this where the larger hose is chosen for routing, heat or fitting availability rather than for extra flow. The O-ring seals on the boss face, so fit it dry and simply nip it up rather than torquing it hard.