This AN12 tee carries male 37° flares on the through run with a female swivel on the side port, so the branch hose can be rotated into alignment before final tightening. At AN12 it belongs on high-volume plumbing: merging dry-sump scavenge lines, splitting a large fuel feed, teeing a surge tank return or branching a big cooler circuit. The swivel side is the practical advantage — with heavy large-bore hose, being able to clock the branch rather than twist the assembly makes the difference between a clean install and a strained one. Bracket the tee where possible instead of letting the hoses carry its weight.