For 50 years now, the Schaller M6 machine head has been a guarantee for reliable tunings. With the locking version, Schaller offers a version of the M6 with a large knurled screw on the back to clamp the string. This means that the string requires fewer axis windings and becomes tuning stable more quickly.
Thanks to LX6 Lube and 18:1 Velvet-Tec, Schaller's M6 135
Schaller M6 135 Locking 3L3R Gold