An aluminium weld-in bung providing a male AN10 flare port. AN10 is genuinely high-flow territory, so this is the size you use for oil cooler feed and return, dry sump scavenge and pressure lines, turbo drains, large fuel feeds and breather plumbing where you cannot afford restriction. Aluminium construction means TIG welding into alloy work such as billet or fabricated sumps, surge tanks, catch cans and header tanks. With a port this size, tack it at opposing points and let it cool between passes, because the larger opening is more prone to pulling out of round. The 37-degree flare seals it, so skip the thread sealant.