I bought this rack tray to house a yamaha mg 124 mixer in a rack case. The reason I went with this and not the rack ears were, for a start it was cheaper then the rack ears but also it gives me room down the side of the desk (that would have been lost with the rack ears) to house my iPod for background music and leave it wired up all the time. The extra space is also handy for storing pens and paper for when people come up looking for something to write a request on.
The build quality is solid and it does it's job perfectly. I used Velcro to stick the desk down into it and the desk doesn't move at all. (I can still pull the desk out if I need to from the Velcro and I don't need to undo any screws)