The PRB-4221 is a right-handed set of RATIO® Calibrated Machine Heads for BASS that use a 2 x 2 configuration.

In order to achieve higher gear ratios, Ratio are the world's first machine heads using a double envelope gear design with a hardened steel gear. Amazingly smooth and super strong.

Gear ratio: unique for each string position - one turn-one tone
Peg holes diameter required: 0.720" (18mm)
String post diameter: 0.547" (13.9mm)
String post length to string hole: 0.807” (20.5mm)
Weight per single machine head: 3.5oz (99.3g)
Weight per set of four: 14oz (397g)
String diameter up to 130 gauge
Includes 4 machine heads, mounting screws and bushings