Graph Tech PRB-5320-B0 Ratio 3+2 Electric Bass Guitar Tuners (Black)Patented RATIO gear technology. RATIO Calibrated tuners incorporate different string gauges into the tuning equation. From bottom B to G 48: 1, 36: 1, 30: 1, 20: 1, 18: 1. We've balanced the gear ratios for each string, simplifying the tuning process. With RATIO, a half turn is a half tone! Each string reacts the same to any tuning adjustment. Predictable and precise tuning on every string. The PRB 5320 is a right handed set of RATIO calibrated tuners