Making use of the Dolos Take-Down System, the Prometheus SC from Pantheon Arms, once installed, enables shooters to switch out barrels and handguards on AR-15-style firearms in seconds. To use the system, simply pull the bottom unlocking tab of the Tri-Lug receiver adapter ring and rotate the handguard, with the barrel and gas system affixed, counterclockwise and withdraw it from the receiver. Installation is in the reverse order. The Prometheus SC provides a 6.5", ventilated handguard, that once installed with Dolos hardware, projects roughly 7" past the receiver. The system is especially useful when switching between firearms that share bolt head dimensions and buffering systems. Price: $200. Contact: Pantheon Arms; (269) 845-1941; pantheonarms.com.