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Open Box Graph Tech 7-String Ratio 4+3 Electric Locking Tuning Machine Heads Level 1 Black 7 String
(1)|Q&A|Item #:M01967004001001
Condition: Open Box - Like NewÂ
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Description
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.
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.

Features
- Includes:
- 7 machine heads, mounting screws, and bushings
- 4 complimentary sets of aluminum mounting plates
Specs
- 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
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Cons
- Fragile bushing not covered under warranty1
- Poor Quality1
Describe Yourself
- Experienced1
Pros
- Functional1
Reviewed by 1 customers
Extreme fragile bushings beware
submitted7 months 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.
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