Part #: 555-0121-467, 5550121467

Introducing a revolutionary new patented device, called the D-Tuna, that enables players to drop from E to D and back, in an instant. Eddie Van Halen has been using it on his guitars for 5 years. It's simple to use and it works. It couldn't be easier to install. You remove the string locking screw from the low E-saddle on the bridge and replace it with one of the 2 D-Tuna locking screws provided, the spring assembly, and the D-Tuna. And that's just about all there is to it. - Edward Van Halen