Charles, The flash hider and bayonet lug have to be the proper distance apart for this bayonet to fit your AR properly. Like James answered. Cut and paste this link on u-tube and get the scoop.----v=hB48RXcGsDU

Yes it'll fit

Depends on the barrel length and gas system length. For most ARs with a carbine length gas system and 16" barrel the ring of the bayonet will hang loosely on the barrel instead of on the flash hider but technically still works. Proper fit would be on a 14.5" barrel with a carbine length gas system, or a 20" barrel with rifle length gas system.

Charles, yes Sir, it will fit the vast majority of AR-15's no issue : youtube.com/watch?v=hB48RXcGsDU