RATIO® patented gear technology. RATIO® - Calibrated Machine Heads incorporate different string gauges into the tuning equation. From Low B to G - 48:1, 36:1, 30:1, 20:1, 18:1. 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-5320 is a right-handed set of RATIO® Calibrated Machine Heads for BASS that use a 3 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.