The EVH D-Tuna is a unique patented device that enables players to drop the E to D and back, in an instant. D-Tuna has been standard equipment on Eddie Van Halen's personal guitars.<br> <br> To install you remove the string locking screw from the low E-saddle on the bridge and replace it with one of the two D-Tuna locking screws, the spring assembly and the D-Tuna.<br> The D-Tuna was designed to adapt to a double-locking tremolo, such as a Floyd Rose or Floyd Rose-licensed version fine tuner tremolo.<br><br> Each D-Tuna kit contains:<br> * 1 EVH D-Tuna Unit<br> * 2 String lock screws<br> * 1 Spring<br> * 1 Fine tuning Allen wrench