Centurion Arms LLC is happy to announce the C4 MLOK® rail.
The MLOK C4 rail system is based off the patented quad rail version. It is a lightweight, rugged, 2-piece free float rail that when installed gives the uppers a continuous 12o'clock rail and MLOK slots for the 3,6, and 9 o'clock positions. The C4 system is the lightest and most rigid rail that clamps to a standard barrel nut on all AR15, M4, and M16 type weapons systems. This design allows the installation of the rail on an upper assembly without removing the front sight post or permanently attached muzzle devices.
Fitting this to a Colt OEM-2 6920 was a dream, literally taking about 10 minutes. Feels great in the hand, solid lockup, speedy shipping, and you can't go wrong with Centurion customer service. A+