Oh I forgot to mention, if your CK gun has a KKM barrel, you will probably have to trim the top front of the mag where it approximates the barrel feedramp by 2-3mm. The earlier MBX mags were shorter here but the new ones, as of when I bought them a year ago, will contact the feedramp and cause malfunctions. Pretty easy to do with diamond files or a dremel. Kinda a pain in the ass but I still like the MBX mag bodies more than STI as you don't have to fiddle with the mag lips. Filing is easier than fiddling to me. If you get them and run into this issue just shoot me a PM and I'll send you photos.