For standard guitars, set of 6. These guitar machines are a triumph in engineering and styling. The housing provides a maximum bearing for worm, gear and string post. Gear ratio is 14 to 1. 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.