Compared to the BM series, a longer string post and a larger button plus a bigger baseplate make it a perfect replacement tuner for JB and PB style bass guitars. Counterfort-mount. All parts are precision-crafted and surface-finished, the self-locking drive ensures an even, delicate and steady tuning. All string posts are made of high-grade brass and fitted into the housing with utmost precision, ensuring the best possible tuning accuracy and wear resistance. Gear ratio 1:20.