I have received the AXX3U5UPRAIL today. They look fabulous, and are of tool-less design. That means, you do not need to put the square rack nut/screw in order to install them.
The only issue I have is they are way too long. My rack is 36 inch deep. These, in their shortest state, is probably 38-39 inch long. So when they are installed with the rack, the rear end will extrude for about 4 inch outside the rack. At
Intel's website, i didn't see the spec listed.
Now I probably have to turn another 90 degree so the rear end will face an open shelf and not be dangerous to anyone who may walk into them. But that will prevent I put the rear screen door on. Another rail I bought is exactly the same length: the AXXPRAIL, an upgrade for 1U/2U, even though the R2312GL4 system I got already came with basic rail. The basic rail's length is just right for my rack, although it lacks the nice, smooth operation from the AXXPRAIL. I guess I will have to live with those mistakes.
So anyone is interested in getting them -- make sure your rack is at least 40" deep, otherwise you will end with some really cool, smooth rails which are too long for the rack.