These steering wheel adaptors are made to adapt the 5 or 6-bolt patterns of a steering wheel to the tapered, splined top shaft of a steering column. All ididit adaptors will fit most ididit columns as well as most 1969 or newer GM passenger car columns and are secured in place with a single nut. A horn wire is included. The 5 and 6-bolt adaptors for Grant and Lecarra come with a horn button. Momo, Dino, Nardi, Diablo and Corvette adaptors do not because the horn button is already included on the steering wheel. Standard size is 2.5" deep.