The EVH D-Tuna is a unique patented device that allows players to drop from E to D and back again in an instant. The D-Tuna has been standard equipment on Eddie Van Halen's personal guitars as well as on Signature Series locking tremolo-equipped guitars since the early 90s. Since then, thousands of D-Tunas have been sold worldwide. D-Tuna is proud to be endorsed by many professional players such as Warren DeMartini (RATT), Michael Wilton (Queensryche), and Dave "The Snake" Sabo (Skid Row) to name just a few. In short... It's easy to use and it works.