A SUS303 stainless inverted seat adapter joining an AN3 line to an M10x1.25 metric thread. The metric side carries a proper inverted seat so the original brake pipe flare seals against a female cone, which is what an AN male flare cannot do in this position — the mismatch is a common cause of joints that weep no matter how tight they are made. The AN3 side takes a standard braided hose, so a metric brake or clutch system can be upgraded without re-flaring pipework. SUS303 stainless was chosen for its resistance to brake fluid and road corrosion in an exposed under-car location. Gauge the port before ordering, since M10 comes in 1.0, 1.25 and 1.5 pitches. Bleed the system fully, then inspect under held pedal pressure before driving.