Lots of 3rd party solutions out there for racking 2 or 3 units together but you're honestly going to want to get this one. It looks classy as hell and affords you a great viewing/operating angle. I'll admit that the MIDI port placements are a bit stupid as a result, but I understand the considerations for euroracking stuff they had to take into account.
I do admit it is a significant cost for what is essentially a couple of pieces of sheet metal, but acknowledging what a low volume item this is to produce I can't really fault the packaging, build quality, or functionality of it.
I do deduct one star due to the fact that Behringer neither offer included, or separately, a 'buffer' to let you rack units of varying widths by extending the rack ears - e.g. you can put a Neutron/K-2/PRO-1 together or WASP/CAT/Model-D together but you can't mix and match the smaller and bigger units in the same rack without 3d printing something or buying a 3rd party solution.