This is a great idea that Eddie Van Halen came up with. I think the Price of $51.50 is a bit steep for a small piece of metal. But if you have a Floyd Rose and need to drop down to D it will get the job done alot quicker. Not sure if it will work with all Locking Tremeolo's.But you could probably email AP Int. to find out.
Price: $51.50 (new)
Where Obtained: Was on Guitar When Purchased (although you can buy alone)
It's really easy to drop down to D with the EVH-Dtuna. Your guitar needs to be set up properly intonation wise. Sometimes you need to tune slightly but its alot easier than having to unlock the nut to get down to D on a Floyd Rose. You just pull out to drop and push back in to go back to standard on the low E. Pretty simple.
It seems like it will last forever but I've only had it for a couple of months. Its worked great everytime I've used it.