Gallery
Description
Features
Specs
Reviews
Q&A
Graph Tech

collapse expand iconDescription

The Graph Tech 7-string Ratio 4+3 electric guitar locking 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 PRL-8521 is a right-handed set of locking Ratio calibrated machine heads for electric guitars that use 4 x 3 tuner configuration. It fits many Gibson, Epiphone and PRS-style guitars, and any other guitar with a 4+3 headstock.

It has a two-pin casing that can be used as is, or with Graph Tech’s InvisoMatch mounting 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.
Graph Tech 7-String Ratio 4+3 Electric Locking Tuning Machine Heads Black 7 String

collapse expand iconFeatures

  • Includes:
  • 7 machine heads, mounting screws, and bushings
  • 4 complimentary sets of aluminum mounting plates

collapse expand iconSpecs

  • Gear ratio: 48:1, 39:1, 24:1, 20:1, 35:1, 20:1, 12:1
  • Peg holes diameter required: 13/32" (10mm)
  • String post diameter: 0.236" (6mm)
  • String post length to string hole: 0.910" (23mm)
  • String diameter up to 72 gauge

Featured Articles

collapse expand iconReviews

3.5

2 Reviews

0%

of respondents would recommend this to a friend

Extreme fragile bushings beware
Extreme fragile bushings beware
Filters
Cons
  1. Fragile bushing not covered under warranty1
  2. Poor Quality1
Describe Yourself
  1. Experienced1
Pros
  1. Functional1

Reviewed by 2 customers

  • God bless!

    5

    submitted4 months ago

    byE

    fromPa

    God and Jesus love you ! Repent ! God bless !

  • Extreme fragile bushings beware

    2

    submitteda year ago

    byJim

    from10538JimC

    I bought two sets of these. They work amazing but there is an issue with the bushings. They are extremely fragile. Mine snapped in half. I sent it back to manufacturer as a flaw. They were horrible. They made me buy a replacement. Bad business practice. I will never buy this again.

  • Previous
  • 1
  • Next

collapse expand iconQ&A

Have a question about this product? Our expert Gear Advisers have the answers.

  • submitted5 months ago

    asked byHaynes

    fromSFV, CA

    Will these fit on a Jackson JS22-7?

    Will these fit on a Jackson JS22-7?

    Open Reply - Gear-Support
    ​No, they won't. The Jackson JS22-7 Dinky features a 3+4 headstock configuration (three tuning machines on the bass side and four on the treble side) . Therefore, the Graph Tech 7-String Ratio 4+3 Electric Locking Tuning Machine Heads (PRL-8521), designed for a 4+3 configuration, would not match this layout. For the JS22-7's 3+4 headstock, Graph Tech offers the PRL-8621 model, specifically designed for this configuration. .​