AN16 sits at the large end of the range, so this straight bulkhead union suits high-volume suction lines, dry-sump tank feeds, radiator and cooler transfers and big fuel system returns where restriction has to be kept low. The extended shank passes through the panel and is secured with a bulkhead nut, giving a tidy sealed pass-through instead of a grommet. Each end is a male 37° flare for standard AN16 female hose ends and adapters. Because of the size, allow clearance for two large spanners either side of the panel and drill the hole accurately — an oversize hole leaves the nut with nothing to clamp against. Bulkhead nut ordered separately.