A large-step reducing adapter that screws into an AN12 male O-ring port and gives you an AN6 male 37-degree flare for the hose. AN12 bosses turn up on sumps, dry sump tanks, oil coolers, surge tanks and fuel cell plates, and it is not unusual to need only a small AN6 feed, return, vent or sender line out of one of them. Sealing is done by the O-ring against the machined face of the boss, so the fitting goes in dry and does not need to be torqued hard into the casting. Flow is limited by the AN6 flare, so do not use it on a main supply circuit.