It's a 19" rack mountable Raspberry Pi B+ case using 2/3U.

NO SLEEVE CASE! Large enough to fit additional cooling and more...

It's also my first thing published and my first ever Fusion 360 project. So if it blows up your printer: Sorryyy! ;)
While this works perfectly for me, I'm always open for hints and suggestions!

There's a non-rack-version, too: https://www.thingiverse.com/thing:2809512