This AN12 bulkhead union is the size you reach for when the line is doing serious volume work: pump suction and return, radiator and oil cooler plumbing, dry-sump scavenge and large-capacity fuel systems. The straight body passes through a drilled panel and clamps with a bulkhead nut, so the hose can be terminated on each side rather than threaded through the hole in one long length. Both faces present a male 37° flare that mates with any standard AN12 female hose end, swivel or adapter. Support the fitting when tightening the mating hose ends so the panel is not loaded, and fit the bulkhead nut (sold separately) squarely against a flat surface.