These are high quality replicas of the 'single-ring' Kluson machine heads fitted to vintage Gibsons in the 50s and early 60s, before Klusons went to 'double-rings'. The colour of the knobs is more authentic (less green!) than the Schaller equivalents and they are a direct fit requiring a 11/32" (9mm) mounting hole rather than the 3/8" (10mm) mounting hole required by the Schaller and Grover equivalents. Set of 6.