This straight adapter joins an AN6 37-degree male flare to an M18*1.5 male metric thread. M18*1.5 is a substantial metric port found on oil galleries, filter housings, sump bosses and cooler sandwich plates, and it is considerably larger than the -6 AN end, so expect the AN flare to be the limiting bore. Choose this fitting where a generously tapped metric port needs to feed a modest circuit, such as a fuel line, a small oil supply or a sender feed, and you want proper AN hose rather than an adapted factory pipe. The AN flare seals dry on metal contact; the metric end seals on its designed washer or O-ring.