This AR-15 complete 6.5 Grendel rifle length upper has a 18" heavy barrel with a 416R stainless finish, and features a 1:8 twist rate, with a mid length gas system. It includes a 15 1/4" MLOK rail, an M4 flat-top forged upper receiver, a bolt carrier group, a flash hider, and a rear charging handle. This 6.5 Grendel upper is compatible with any mil-spec AR-15 lower. This has the new handguard.