This BCA AR-15 complete 5.56 Nato pistol length upper has a 4.5" heavy contour barrel with a parkerized finish, and features a 1:7 twist rate, with a micro length gas system with .875 gas block. It includes a 4" MLOK rail, an M4 flat-top upper receiver, a BCA bolt carrier group, a flash hider, and a rear charging handle. This 5.56 Nato upper is compatible with any mil-spec AR-15 lower.Shop more 5.56 NATO Uppers!Magazine not included. Check out Magazines here!Check out our Ammunition Recommendations! It is the responsibility of the consumer to ensure all state, local, federal, and ITAR regulations are followed.* Note - We strive to provide the most accurate photographs of our product. Variations may occur in the skeletonized section of the handguard/flash hider you receive.Attention SignWARNING: This product can expose you to chemicals, such as lead and other petroleum products, which are known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to the California P65 Warning site.