This set consists of two clamps, complete with screws and T-Nuts and can be used to clamp the 4-jaw chuck to the milling table or lathe crosslide. The set provides a little more versatility than the chuck-to-T-slot adapter (P/N 1187) in that the chuck can be located almost anywhere on the table, and the part can be properly aligned with the axis of the machine. The clamps fit in a groove machined around the circumference of the 4-jaw chuck. They are the same as those furnished with the Sherline milling vise (P/N 3551), so they are not needed if you already own a vise.