This listing is for a single Right hand side Original Ford Kelsey Hayes Disc Brake Caliper for EITHER a 1965 1966 or a 1967 Mustang and would have been on the factory disc Brake cars like the GTs and the Shelby.
The 1965 1966 has the smaller 5/16" input hose size and the 1967 has the larger 3/8" hose opening.
Both Calipers have been rebuilt. Both have the original K/H markings on both halves of the caliper.
I need to know which one you want to ship.