Grover Rotomatic Guitar Tuning Machines - 14:1 Ratio - 3 per side - Nickel Worm and gear are precision-cut for perfect meshing. This eliminates backlash and slippage Countersunk tension screw permits players to regulate turning tension to any degree. Gear box has a special lubricant for lifetime, trouble-free service. Includes 5/8' washers, bushings and wood screws; Hole Size = 25/64"; Gear Ratio is 14:1 Nickel