Grover Machine Head Tuners - Black Chrome. Three left-Three Right Original Rotomatics. These guitar machines are a triumph in engineering and style. The housing provides a maximum bearing for worm gear and string post. Gear Ratio is 14:1. Worm and gear are precision-cut for perfect meshing. This eliminates backlash and slippage. Countersunk tension 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