The Adams Arms AA-15 features the Adams Arms piston conversion kit as a factory-installed upgrade, providing a cleaner-running gas piston AR-15 at a price competitive with direct impingement premium builds. Type: Semi-Auto Rifle Action: Gas-Operated Caliber: 5.56x45mm Capacity: 30 Year introduced: 2013, USA Weight: 7.1 oz Overall length: 35.5" Status: Active Intended use: Tactical, Home Defense