A stainless weld-in bung producing a male AN6 flare port. AN6 covers most standard-duty plumbing: fuel feed and return on street and mild performance engines, oil lines, power steering return and coolant bleed runs. Choose stainless when the vessel you are welding into is stainless, or when the port lives in a harsh spot where corrosion resistance matters more than weight, such as an exposed underbody tank on Highveld or coastal roads. Weld with matching stainless filler and manage the heat so the flare seat stays flat. The 37-degree flare on the mating AN6 hose end or adapter does the sealing, so avoid thread tape and do not over-tighten.