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7 STRINGS: 7-in-line Electric Locking Machine Heads (PRL-8721-C7, Select Finish)

7 STRINGS: 7-in-line Electric Locking Machine Heads (PRL-8721-C7, Select Finish)



Regular price $187.77 USD
Regular price Sale price $187.77 USD
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RATIO® patented gear technology
RATIO® - Calibrated Machine Heads incorporate different string gauges into the tuning equation.

From Low B to High E 48:1, 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-8721-C7 is a right-handed set of Locking RATIO® Calibrated Machine Heads for electric guitars that use 7-in-line tuners.

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.


6-in-line 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: 0.581lbs (266g)
String diameter up to 72 gauge
Includes 7 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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