A stainless weld-in bung giving a male AN12 flare port. AN12 is used where restriction has to be kept to an absolute minimum: dry sump scavenge, oil cooler plumbing on high-output engines, crankcase breather and vent lines, and big surge tank or swirl pot connections. Stainless is the choice when the fabrication is stainless, or when the port faces heat, damp or coastal conditions and long service life matters more than saving grams. Weld with matching stainless filler and stage your passes, because a large-diameter port distorts easily under concentrated heat. Fit any AN12 hose end without sealant and do not over-tighten the 37-degree flare.