Wilwood Engineering Polished Aluminum Duel Master Cylinder. This master cylinder features Polished aluminum finish with black anodized machined aluminum top. Master cylinder has a 1 1/8" bore and includes ports on both sides to work with all applications. Master cylinder outlets are 1/2-20 UNF and come with adapter fitting for 3/8-24 and 9/16-20. Master cylinder works with both disk/drum or disk/disk applications just change proportioning valve to match your set up. We also offer proportioning valves, boosters, brackets and brake lines.