Kluson KF6BL Series guitar tuners are the 6-in-line locking version of their F6B. KF6BL machine tuners give you a 6-in-line version of the tight performing machine tuner including the high 15:1 gear ratio. The KF6BL tuner uses the same locking mechanisms as the BL series. The KF6BL locking 6-on-a-side tuner set includes matched plating colors on the tuning mechanism knobs for enhanced appearance on lighter colored headstocks. 12/64" shaft size. Now you can retrofit your vintage guitar with no modification.