Graphtech Ratio 6 String 3+3 Bass Y-Style Button Black PRB-6330-B0 

Graph Tech's calibrated & synchronized tuning system makes tuning and re-tuning your bass faster and more intuitive. Tuning on the fly has never be easier!. Each string position has  it's own calibrated gear ratio, so every string feels and reacts the same to any tuning adjustment.

One full rotation of any key results in a one full tone pitch change (give or take).  From Low B to C,  the gear ratio's are 48:1, 36:1, 30:1, 20:1, 18:1 and 16:1. 

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