Contrary to the previous review, I had no problem mounting this to a G&G Combat Machine which I used as a base gun in my project. GI even uses them for making Diablos, so I was weary while deciding on whether to buy this or not, but I did and it fit well. The thing is that you can't just screw it on out of the box. The barrel nut is pre-screwed into the upper body mount, but all you have to do is take off the rails, unscrew the barrel nut, insert the barrel, then screw on the upper body mount. Once you've done that, you can tighten the barrel nut onto the upper body mount. Luckily for me, Madbull included some very detailed instructions on how to mount this.
It was very easy to mount and it is extremely lightweight. You can't go wrong with this one. All together, my rifle ended up being 25 inches long with the stock collapsed. It is shorter than an Mp5a4. If you are looking for a high quality rail system that is easy to install out of the box.
Three QD sling mount ports.
Utilizes a 225-229mm barrel perfectly. (not included.)
Great matte finish.
No wobble once installed correctly and rails are mildly tightened down.