The Troy MRF is the strongest user-installed free-floating rail system in the world. Troy MRFs are available for all M16/M4 weapon systems equipped with the original factory barrel nut. The MRF"s patented mounting system reinforces the barrel nut with a sturdy clamp and anti-rotation alignment lugs. Troy MRF BattleRails provide an uninterrupted rail extension and hand guard aligned perfectly with the host weapon"s flat-top receiver.- ARMALITE - Flat Dark Earth