GraphTech RATIO Open Back Acoustic 3+3 Butterbean ~ Nickel

The PRN-3422 is a right-handed set of open-back RATIO® Calibrated Machine Heads for acoustic guitars that use 3+3 side tuners.

It has a Butterbean button.

3+3 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: 0.346" (8.8mm)
String post diameter: 0.236" (6mm)
String post length to string hole: 0.827"; (21mm)
Weight per single machine head: 0.055lbs (25g)
Weight per set of six: 0.331lbs (150g)
String diameter up to 72 gauge
Includes 6 machine heads, mounting screws, and bushings