This AR-STONER LR-308 complete rifle length upper has a 12" barrel, and features a 1:10 twist rate. It includes the MLOK Slim Rail, an M4 flat-top billet upper receiver, an AR10 bolt carrier group, a flash hider, and a rear charging handle. This upper is compatible with 1st gen DPMS low profile lowers. FeaturesSlim Mlok Free Float Hand Guard.750 Gas Block.308 Mil-Spec Charging Handle Alum..308 Dust Cover