This adapter screws into an AN12 male O-ring port and offers an AN8 male 37-degree flare for the hose end. AN12 bosses are typical of sumps, dry sump tanks, big oil coolers and fuel cell plates, and this is the fitting to use when only an AN8 circuit is being run from one of them, such as a cooler feed, a scavenge branch or a high-output fuel supply. Sealing happens at the O-ring on the boss face rather than on the threads, so the fitting goes in dry and does not need heavy torque. The AN8 flare determines the flow capacity of the connection.