A right-handed set of Ratio Calibrated Machine Heads for acoustic guitar that use three per side tuners. It has a two pin casing that can be used as is, or with our InvisoMatch mounting plates. 4 Sets of InvisoMatch mounting plates in brushed aluminum are included to make installation on most guitars fast and accurate by using your existing screw mounting holes. Color matching plates are sold separately on Amazon or GT website. Ratio - Tuned Machine Heads incorporates the different string gauges into the tuning equation. From Low E to High E 39:1, 24:1, 20:1, 14:1, 20:1, 12:1. We balanced the gear ratios to each string simplifying the tuning process. With Ratio, a half turn is a semi-tone! Every string reacts the same to any tuning adjustment. Predictable, precise tuning, on every string. Gear ratio: unique for each string position - one turn-one tone. Peg holes diameter required: 13/32" (10mm). String post diameter: 0.236" (6mm). Main post diameter: 0.385” (9.8mm). String post length to string hole: 0.890” (22.6mm). Weight per single machine head: 1.06oz (30g). Weight per set of six: 6.31oz (179g). String diameter up to 72 gauge. Includes a set of machine heads, mounting screws and bushings. Includes complimentary 4 sets of aluminum mounting plates.