The Dolos, (Greek god of deception), is a revolutionary new product that allows the user to quickly remove their barrel, or change calibers, in seconds on their AR-15 rifle or pistol with no tools. There are other takedown systems on the market, but none can compete with the Dolos in terms of speed, handiness or repeatable accuracy after a barrel change. The new Dolos Gen2 incorporates a locking mechanism to prevent barrel from backing off. To break the rifle or pistol down, simply lock the bolt to the rear, disengage ratchet lock, turn the handguard and pull the barrel assembly straight out of the receiver. To reinstall the barrel, insert it into the receiver and twist the handguard. The kit comes with updated lock ring, ratchet housing assembly, and set screws. Installation takes only a few minutes and the Dolos is compatible with any mil-spec AR-15 upper. The kit is designed to work with any carbine or pistol length direct impingement gas system. The system is designed to work with any Yankee Hill Machine thread pattern handguard. The kit is designed to work only with direct gas impingement systems and is not compatible with gas piston conversions. The Dolos works fine with railed gas blocks on carbine length or longer barrels. NOTE: Firearm, barrel, gas block and gas tube are NOT included. Please note a handguard is NOT supplied with this kit to allow you to add your handguard of choice!!