Excellent quality and fitment. Unlike with some other Lego copies there were no wonky build steps with pieces being barely supported. The design was well thought out and it was a lot of fun to build. Extending and collapsing the stock works differently from the original and is not as quick, but that's probably due to the limitations of the plastic. Apparently you can also shoot rubber bands with it, but I haven't tried that feature yet. Size wise, it's pretty much identical to a real MP5, as shown in the comparison picture with my MKE T94 (Turkish licensed copy of the H&K MP5) on top.
I forgot to mention, the magazine release is actually functional and the magazine can be removed and inserted, just like on the real MP5. Unfortunately the charging handle and the sights aren't as close to the real thing, but for a 20EUR display piece, that's more than one can ask for.
it works great! took me a while to actually build it but its super cool!