Part of the Ratio Electric Series, this six-pack of 3x3 Graph Tech PRL-8311 machine heads features advanced Ratio Electric tech to ensure smooth, accurate and ultra-stable tuning. This patented system basically ensures that every tuner adjusts the pitch at the same rate, meaning that a half-turn raises or lowers the pitch of every string by around a semitone. These are also locking tuners, so after the string is threaded through, it's can be locked in place by turning the thumb screw on the back of the machine head, and once you've given your strings a stretch, they can be tuned with surgical precision. The Graph Tech PRL-8311 tuners feature contemporary buttons and are easily mounted via a two-screw system, but can also be combined with one of the four included InvisoMatch mounting plates to adapt them for headstocks that are already set up for different screw systems.