This set of six sealed-gear black skull tuners is the perfect accent for your new instrument build, or as a replacement for an existing guitar repair job. They are set up for use on a "6-in-a-Line" headstock (such as a Fender(tm) Strat(R) or Telecaster(R)-style electric guitar. This set includes all necessary mounting hardware: screw-in bushings, washers, and mounting screws. They are intended for headstocks that are between 0.46" (11.72mm) and 0.65" (16.5mm) thick. A good rule of thumb is 1/2" to 5/8" thick, with 9/16" being the ideal. Trying to use these with thicker or thinner headstocks may not work. If you are looking for a unique, distinctive tuner/machine head style for your guitar, then look no further!