The Defender Standard Model 16 features: - Standard Flattop Upper Receiver. - 16 Chrome Lined 1:7 Twist Government Profile 5.56 Barrel. - Standard Semi-Auto Bolt Carrier Group. - Tactical Charging Handle Assembly. - Defender Lower with SOPMOD Buttstock. - Standard Trigger Group. - Tactical Adjustable Rear Sight - (1) Heavy Duty Push Button Swivel (Included as of 2011 orders). - (1) Thirty Round Magazine. - Ships with a Sling and Operators Manual. - Specs: - Direct gas impingement - Overall length with SOPMOD collapsed: 33.25 - Overall length with SOPMOD extended: 36.25 - A2 Birdcage Compensator - 1/2 X 28 thread pitch - Cryogenically treated barrel to increase accuracy barrel life and easier cleaning - Electronically tested and recorded trigger pull