OEM C9AZ-2140M brake master cylinder has two mounting holes. The function of the holes are outleting the brake fluid. The size is 1/2-20" & 9/16-18". The other reference numbers are C9AZ-2140M, 18M1020, 13-1485, C9AZ2140D, E73323, 13-1485. It fits for 1967-1970 Ford Mustang.
