AN6 is the size most fuel systems are plumbed in, and fuel lines are exactly what usually has to cross a firewall or boot divider — which makes this one of the most-used bulkheads in the 833 range. The fitting seals its own hole in the panel, so there is no chafing against a bare edge, and the 90-degree body turns the hose immediately on the far side where space behind a panel is normally tight. Male AN6 flare threads on both ends suit standard AN6 hose ends, with the extended thread taking a matching AN6 bulkhead nut. Deburr the hole before assembly.