With the all of the free float rail systems currently being offered for the AR15 and M4 weapon systems, the Centurion Arms LLC gas block is small enough to fit under most rail systems. These gas blocks are the best replacement on the market for the fixed sight tower that comes standard on the AR/M4 system.
The gas block covers less than one inch of the barrel's surface and is made to extremely tight tolerances. These gas blocks are in matte black finish. They also have a flat area machined into both sides toward the bottom of the gas block to help facilitate proper pinning of the gas block to the barrel.
All current models are made to fit barrels that feature a .750 diameter at the gas block.