An AN6 double-male flare union for coupling two AN6 female hose ends or ports. AN6 is the most common size in performance fuel plumbing, so this is the union most builds actually need: it lets a long feed or return run be made up as two shorter hoses, joins a hard line to a flexible section, and gives a clean disconnect point at the firewall or under the boot floor when a tank or pump has to come out. Both ends seal on the 37° AN flare cone, metal to metal, so no thread tape or sealant should be used. Keep the union somewhere accessible rather than buried behind a subframe, clamp the hose on both sides so the joint carries no weight, and tighten to snug plus a light nip.