A reducing straight adapter threading into an AN16 male O-ring port and presenting an AN10 male 37-degree flare. AN16 bosses appear on dry sump tanks, large oil reservoirs, coolant fittings and fuel cell plates, where an AN10 branch for a cooler feed, a scavenge line or a return is often all that is required. Doing the step in one fitting keeps the joint count and leak risk down compared with stacked reducers. The port seals on its O-ring against the boss face, so no thread sealant is used. Flow through the connection is governed by the AN10 flare rather than the larger port.