The Graph Tech Ratio 3+3 electric guitar tuning machine heads incorporate different string gauges into the tuning equation. Graph Tech 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 adjustments, delivering predictable, precise tuning on every string. The Graph Tech PRN-2341 is a right-handed set of Ratio calibrated machine heads for acoustic guitars that use 3 x 3 tuners. It has a two-pin casing that can be used as is, or with Graph Tech’s InvisoMatch mountain plates. Four different 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.