A stainless SUS303 adapter joining an AN3 line to an M10x1.5 metric port, the coarse pitch of the M10 family. It appears on certain callipers, unions and cylinders, and this adapter is how you run AN3 braided brake or clutch hose to them without altering the original component. SUS303 stainless was selected for corrosion resistance, sensible for a fitting that spends its life exposed to brake fluid, water and road salt. Because M10 ports exist in 1.0, 1.25 and 1.5 pitches and all three feel plausible for the first turn, gauge the port rather than trusting appearance — a stripped calliper thread is not a cheap lesson. Bleed the system fully after fitting, then inspect the joint under sustained pedal pressure before the vehicle goes back on the road.