I was very happy to receive this piece, and eager to try it out.
Unfortunately, at first, I only had a KJW G19 magazine on hand. The magazine was too large for it, the sliding grooves were just slightly too far apart : that means you can put it on your magazine, and it might look like it's a good fit, but it does not really catch onto it and when you try to pull the magazine out, the magazine base will be pulled away.
I thought that it was perhaps because the magazine I used wasn't the right model.
I found a TM G17 magazine, hoping that the issue could be resolved this way, and unfortunately, it was still the same issue.
HOWEVER, since the sizing is just very slightly off, it can be quite easy to fix. With a thin layer of duct/gaffer tape in the grooves (or even just one of the sliding grooves), I believe that it will add enough extra thickness for a good and snug fit.
Also, the piece is quite well made, and the trademarks are very precise and accurate.
Not perfect out of the box, but a beautiful piece that, with a little bit of simple tinkering, can be put to good use.