The adams arms p1 model includes adam's picatinny railed gas block with 3 adjustable settings and m4-style furniture.The p1 is your piston driven foundation, ready to be customized to fit your needs.Action: Semi-AutoCaliber: 5.56x45mm NATOBarrel Length: 16"Capacity: 30+1Trigger: Standard G.I.Oal: 32.50"Weight: 6.99 lbsStock Description: 6 Position CollapsibleMuzzle: A2 Flash HiderReceiver Material: AluminumSights: Optic ReadyBarrel Description: 4150 Chrome Moly Vanadium M4 ProfileTwist: 1:7"Barrel Length Range: 16" to 16.99"Weight Range: 6 lbs to 6.99 lbsHand: RightStock Finish Group: BlackMetal Finish Group: Blued/Black