This straight adapter mates an AN12 37-degree male flare to an M18*1.5 male metric thread. M18*1.5 is a good-sized metric port, common on oil galleries, cooler sandwich plates, sump bungs and larger sender bosses, and it pairs well with -12 AN because neither end unduly throttles the other. That makes this a strong choice for oil cooler feed and return lines, dry sump plumbing and high-volume transfer work. The AN flare seals metal-to-metal and must be assembled clean and dry, while the metric end depends on the correct sealing washer or O-ring at the shoulder. Check the port’s sealing method before fitting, as they are not interchangeable.