Kluson? Adapter Bushing Set For Deluxe Or Supreme Series Tuning MachinesThese Kluson? steel adapter bushings are available in 2 types 6 mm version for use in converting a modern 10mm drilled headstock to accept vintage Kluson? stamped steel tuning machines with the metric 6mm string post diameter used between 1995 and 2006.1/4 in. version for converting a modern 10mm drilled headstock to accept vintage Kluson? stamped steel tuning machines with the original US 1/4 inch string post diameter. Many repair shops use these to convert a vintage instrument back to original peg head specs.