A stainless weld-in bung producing a male AN4 port. The AN4 size handles the light-duty plumbing on a build: pressure gauge and sender feeds, boost and vacuum references, clutch lines and small oil feeds. Stainless earns its keep where the host vessel is stainless, or where the port lives in a wet, road-salt or high-heat area and long-term corrosion resistance matters more than saving weight. Weld it into stainless with matching filler and control your heat input so the 37-degree seat does not pull out of shape. Once installed, thread on any AN4 hose end or adapter; the flare does the sealing, so no thread tape or sealant is needed.