The D'Addario Equinox headstock tuner precisely tunes guitars, basses and other stringed instruments utilizing vibrations rather than sound. Using a highly sensitive piezo sensor and large multi-color display, the Equinox Headstock Tuner allows you to tune easily and accurately in noisy and dimly lit environments where many other tuners fail. The tuner features a pivoting display. This 4-pack includes two black finished Equinox headstock tuners, and two that have a white finish, so you can have one that matches your style.