The SD series combines "Rock-solid" technology and the post collar or: "Self-Center Guide", found on enclosed gears in the base plate of the gear allowing the post to perfectly align itself with the bushing which attaches the gear to the headstock. The SD series uses a torque balancer to ensure steady rotation of the tuner button giving a high-quality sound performance as well as great functionality. Through its use of the ideal materials selected for each component part, you also obtain a far superior sound. Mounting hardware included: bushings, washers, and screws. Made in Japan. Gotoh Packaged.