This straight adapter carries an AN4 male 37-degree flare on one end and an AN4 male O-ring port thread on the other. The port end uses a straight thread with a captive O-ring, so it seals against the face of the boss rather than by wedging tapered threads together, which means no thread tape or sealant and no risk of splitting a casting. AN4 is the small-bore size, so it suits turbo oil feeds, oil pressure sender and gauge lines, clutch and brake plumbing, and boost reference lines. Check that the component you are fitting into is genuinely an O-ring boss and not NPT before ordering.