Graph Tech PRB-4221-C0 - 4 String 2+2 F-style Bass Ratio stemmeskruer - Chrome

RATIO® patented gear technology
RATIO® - Calibrated Machine Heads incorporate different string gauges into the tuning equation.

From Low E to G - 48:1, 36:1, 25:1, and 23:1.

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. 

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.