I've got one on my Fulton Armory AR and, if I had to do it all over again, I would've bought a KAC RAS. At the time, no one else was offering a FF RAS so it suited my needs. The one I have is from the first batch they made and the sub-contractor that made them didn't made the picatinny rails exactly to spec. The problem is the distance from the surface of the tube to the under side of the rails is a wee bit too short. I had to file out a bit on my KAC foregrip to make it fit and an adaptor I bought for my HK UTL light won't even go onto a rail period. Even when I get the KAC vert. foregrip one, it doesn't lock down exactly as it is supposed to but it feels solid enough. It is a bitch to slide the foregrip on especially when compared to another rail I have on another rifle. This might also explain why KAC rail panels are tough to get locked on. Also, the carbine length RAS is a bit too long to be completely covered by a 6 panel KAC cover (good one C-More).
BTW, I spoke with C-More directly about this problem and the info I am passing along to you is EXACTLY what they told me. The first gent I s/w said they first units were "defective" (that is the exact word he used) The second gent I s/w said they were not "defective" but the first units were not the exact spec they requested. When they received the first units from the sub-contractor (that manufactured the RIS for them), they discovered the problem. The folks at C-More said they tried every rail accessory they could get their hands on and they were aware of the "minor" problem with the KAC foregrip but they stated that everything else they tried worked fine. FWIW, my M-900A is rock solid but it's a bit more finicky getting it on the rail when, again, I compare it to another RIS I have. I also have a KAC RAS sling adaptor on the C-More and it's rock solid.
So, for now, I'm living with it. It works fine for my purposes but to be blunt, I'm still pissed off about the whole thing. I will never ever ever buy another C-More product ever again nor will I ever recommend any of their products to any one. I'll probably get around to replacing it someday with a KAC but since it's a pain in the butt to replace most RAS, I'm holding off for winter so I won't miss my AR while it's at the smith.
I guess for cheap money ($50-$100), it would be a good deal. I'll probably sell mine for $50 when I get around to replacing it.
Finally, they folks at C-More said the next batch (due this spring or summer) will no longer have this problem. I guess what really ticks me off is they wouldn't replace it or offer me anything to make me happy. I've got better things to do than slander them 24/7 but you asked so I'm giving you my experience which was less than satisfactory. F' them and their rail system. They obviously don't care about their customers and they probably don't sell enough of their Quad rails to care. I really don't like saying such negative things about any manufacturer but I REALLY hate getting screwed.