For what this is, a sheet of steel with a a few bits, it's very, very, very expensive.
However, my recording rig is portable, so I needed to secure my GAP Pre 73 in a rack case. I tried drilling holes in a cheap no-name rack tray but it proved to be more work than it was worth. Having bought this rack-kit, my GAP is safe and secure in its rack space.
It's quite heavy and very sturdy. The paint job is thick and seems to be quite tough. And that's about it. Once you put it in your rack, it disappears and you never notice it again.
If you need to rack-mount your GAP gear AND travel with it, maybe this is a sound investment. But if you don't move your gear around frequently, I'd spend the ¤59 on something you might get some fun out of.
As an aside, the guy who runs WARM Audio posted on one of the forums that the WA12 fits this rack-kit perfectly. I haven't tried it myself, but it might be useful info for someone looking to mount their WA12.