Bushmaster M4 Flat Top AR15 Complete Upper Assembly - Black | 5.56NATO | 16" Barrel | A2 Handguard | A2 Flash Hider 00-40008-BLK 0040008BLK

Specifications: - Caliber 5.56 NATO (.223 REM) -16" Barrel with a 1:7 Twist Rate - M4 Style Handguard  - Flip-UP Rear Sight  - Salt Bath Nitride Bolt Carrier Group -MPI Tested Bolt - A2 Birdcage Flash Hider 1/2 x 28    Features:  -The gas system is carbine length - 7075 Forged A4 Flat top - F-Marked sight base for sight alignment, providing correct carbine sight alignment   Proudly Made In U.S.A.  Manufacturer Part Number: 0040008BLK