We had these made for us with a pinned FSB using a Circular Handguard Cap. This means that this barrel is compatible with the Mid-Length Magpul SL Handugards and most other drop-in handguards. Get one with a VG6 Epsilon pinnable Muzzle Brake for a 16 overall length.Barrel SpecsBrandBallistic AdvantageLength14.5Chamber5.56 NATO (shoots both 5.56 NATO and .223)ProfileGOVT / SOCOMFinishQPQ NitrideBarrel Steel4150V Chrome MolyTwist Rate1:7Gas System LengthMid-LengthGas Block Journal.750Feed Ramp ExtensionM4Muzzle1/2 X 28Weight25oz