Ratio Electric Locking MusicMan 4x2 MiniCon Button (Select Finish) - Graph Tech Guitar Labs Ltd.

4+2 Ratio Lefty Electric Locking Machine Heads Mini Contemporary Button (Black Finish) (PRL-8421-LB0)



RATIO® patented gear technology
RATIO® - Calibrated Machine Heads incorporate different string gauges into the tuning equation.

From Low E to High E 39:1, 24:1, 20:1, 35:1, 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.

RATIO Machine Heads explanation video



The PRL-8421-LB0 is a left-handed set of Locking RATIO® Calibrated Machine Heads for a Music Man, or other 4 x 2 style headstock.

It has mini contemporary button.


It has a two pin casing that can be used as is, or with our Patented InvisoMatch Mounting Plates [opens in new tab].

4 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.


4x2 tuners set  Ratio Tuned Machine Heads: The New Standard In Tuning Technology



Gear ratio: unique for each string position - one turn-one tone
Peg holes diameter required: 13/32" (10mm)
String post diameter: 0.236" (6mm)
String post length to string hole: 0.910” (23mm)
Weight per single machine head: 0.083lbs (38g)
Weight per set: 0.496lbs (225g)
String diameter up to 72 gauge
Includes 6 machine heads, mounting screws and bushings
Includes complimentary 4 sets of aluminum mounting plates


Staggered Ratio Measurements.pdfRatio Installation Guide.pdfRatio Installation Guide Video


Moss Hart

Reviewed in the United States on February 15, 2020

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