An aluminium weld-in bung giving you a male AN6 flare port. AN6 is the everyday workhorse size on street and club-level builds: fuel feed and return on a naturally aspirated or mildly boosted engine, power steering return, oil feed and gauge plumbing. Being aluminium, it is intended for TIG welding into alloy fabrications such as sheet or billet surge tanks, header tanks, catch cans and aluminium sumps, so do not try to weld it into steel. Tack in a cross pattern and let it cool between passes to keep the port round. Any AN6 hose end threads on and seals on the flare, so leave the thread sealant in the drawer.