Graph Tech - Ratio Tuned Machine Heads - Guitar Tuning Machines - PRN-4411-N0 Ratio Tuned Machine Headsare the first and only machine head to incorporate the different string gauges into the tuning equation. Includes (6) Bushings, (6) Mounting Screws, (6) Washers and installation instructions. Nickel, contemporary shaped button; 3-Per-Side; Offset screw casing Model: PRN-4411-N0 Available at Ant Hill Music !