For anyone with this shallow rack that has threaded holes. Don’t bother with any adapters, just use a dremel to cut the little hooks off each side of the rails, and then screw the rails into your rack. Done…
I went to buy the disk for my dremel at my local Ace, one of the guys there just took it in back and cut it down for me for 5$. “Ace is the place”
I have an ECHOGEAR 20U rack and was pretty bummed when I found that the rails wouldn’t work, even with the adapters… until I discovered that there are numbered square holes on the ‘sides’ of the rack. I just rotated my entire rack 90 degrees and mounted everything with rack studs, worked pretty great!
That is also an excellent way forward! 
I wasn’t about to do that… easier to cut off the ears lol
