This reducing adapter screws into an AN12 male O-ring port and provides an AN10 male 37-degree flare for the hose. It is a natural pairing on oil systems, where sumps, dry sump tanks and large coolers carry AN12 bosses but the pump, cooler or drain circuit is plumbed in AN10. Because it is only one size step, the restriction it introduces is minimal for most oil and fuel work. The straight thread seals on its O-ring against the machined face of the boss, so it is fitted dry with no sealant and can be clocked to suit hose routing before final tightening.