The Schaller M6 Machine Tuning Heads with 12:1 ratio, sealed lubrication, adjustable knob tension, cast housings, threaded hex peghead bushings and removable metal knobs are hand-polished and manufactured to the highest quality standards. All Schaller M6 tuners require 10 millimeter (13/32 inch) diameter pegholes. Sold in sets of 6, with mounting screws, threaded bushings and washers included.