This alloy AN banjo mates an AN4 outlet to a 12.5mm eye, so it fits ports designed around an M12 banjo bolt. It is a common requirement on engines where the factory port is a generous M12 but the line being run is a small-bore feed or sensor supply that only needs AN4. The rotating banjo body means you can bring the hose in at whatever angle keeps it clear of manifolds and belts, which a fixed straight fitting cannot do. Assemble with a sealing washer on both faces of the eye and torque the bolt evenly. Match the bolt thread pitch to the port before fitting.