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6-In-Line Ratio Electric Guitar Machine Heads (PRN-2721, 2731, Select Finish and Button Style)

6-In-Line Ratio Electric Guitar Machine Heads (PRN-2721, 2731, Select Finish and Button Style)



Regular price $114.99 USD
Regular price Sale price $114.99 USD
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Select Finish
Select Button Style

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 PRN-2721 and PRN-2731 are a right-handed sets of RATIO® Calibrated Machine Heads for electric guitar that use 6-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: 0.890” (22.6mm)
Weight per single machine head: 0.066lbs (30g)
Weight per set of six: 0.393lbs (179g)
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

Amazon Verified Purchase


Rated 4.7 stars
Based on 3 reviews
Total 5 star reviews: 2 Total 4 star reviews: 1 Total 3 star reviews: 0 Total 2 star reviews: 0 Total 1 star reviews: 0
100%would recommend this product
3 reviews
  • RG
    Robert G.
    Verified Buyer
    I recommend this product
    Rated 5 stars
    3 months ago
    Singer/Guitar Fiend

    These tuners have no equal and I would put them on all sixteen of my guitars if I had the capacity to do so.

  • KA
    Kevin A.
    Verified Buyer
    I recommend this product
    Rated 5 stars
    3 months ago
    Top quality

    I bought these machine heads as part of a full restoration on my early/mid 80s BC Rich Warlock NJ series electric guitar. Although I am still in the rebuild process I can tell these are of very high quality. They were the exact replacement machine heads with no drilling necessary. Can't wait to finish the rest of my rebuild and will review again with pics of the final results. Thank you GT for making a great product! -KA

  • BG
    Brian G.
    Verified Buyer
    I recommend this product
    Rated 4 stars
    5 months ago
    almost perfect

    the machine heads are a perfect 10. the bushings and washers are a 6. The quality is not great, especially considering the price.. . I took the bushings and washers from some unused hipshots (they are too short) since they are higher quality and now the machine heads are perfect all around.

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