The PRL-9721-B0 is a set of offset post-ratio locking tuned machine heads for an electric guitar in an in-line 6 configuration. They have 3 different heights, contemporary buttons, 2 pin housing and are finished in black. *Now includes standard InvisoMatch mounting plates for easy installation. Fits most dolls. Adjusted Ratio Machine Heads are the first and only machine head to incorporate the different string gauges into the tuning equation. Graph Tech has balanced the individual gear ratios for each chain, greatly simplifying the tuning process. No more overshooting the G string or twisting on the high E string. With Ratio, every half turn of a key is equivalent to a semitone change on all strings! Faster, more precise tuning on every string.