Graph Tech RATIO Adjustment Machine HeadsRatio Tuning Heads are the first and only machine head to incorporate the various gauges into the tuning equation. We have balanced the individual gear ratios at each chain, which has greatly simplified the tuning process. No more going over the G string or hijacking the high E string. With Ratio, every half turn corresponds to a semitone change on all strings! Faster and more precise adjustment of each chain.