Grover Rotomatic 305C guitar tuning machine heads are a marvel of engineering and design. These are mid-size Rotomatics with a gear ratio of 18:1 and a housing that provides optimal bearing for worm, gear and string post. Precision-cut worm and gear serve up perfect meshing, eliminating backlash and slippage. A countersunk tension screw lets you customize tension to your personal preference. The Rotomatic's gear box is permanently lubricated, giving you a lifetime of trouble-free operation. 5/8" washers, bushings and wood screws are included with this set of six Grover Rotomatic 305C guitar tuning machine heads.