Kluson meccanica tpkmb3-c TonePros® under license from Kluson® has successfully combined the classic styling of the original Kluson® 3 + 3 design in a die-cast housing. Utilizing the same footprint and mounting screw pattern, TonePros® offers you several different options to either retrofit your vintage instrument with little to no modification or upgrade your modern instrument. This 15:1 ratio, die-cast 3 + 3 set of tuning machines has a hex-head screw-in bushing (or commonly known as a bolt bushing) and the highly desireable Kluson metal Keystone button as used on Klusons Premium die-cast tuner known as the Waffleback. This requires a 10mm (25/64 in.) peghole for installation.