An AN12 double-male flare union for joining two AN12 female hose ends or ports. At AN12 the plumbing is typically dry-sump scavenge, breather and vent routing, big cooler circuits or high-demand fuel feed, and long runs in these sizes are much easier to build and fit in two shorter sections than one continuous hose. A union also gives you a deliberate break point for servicing. Both ends use the 37° AN flare seat, which seals metal to metal — thread sealant is neither needed nor wanted. Because AN12 hose is stiff and heavy, mount or clamp the hose on both sides of the union so its weight is carried by the chassis rather than by the joint, and tighten to snug plus a light nip rather than leaning on the spanners.