15/16" late model aluminum master cylinder from Dr. Diff. Manual brakes on both my Challenger and my Duster, the Challenger has 11.75" mopar disks from a B/R body and 11x2.5" rear drums, the Duster has Dr. Diff's 13" cobra kit up front and 11x2.5" drums out back. Both work great with the 15/16" m/c.
