The Phalanx CIWS is a close-in weapon system for defense against airborne threats such as anti-ship missiles and helicopters. It was designed and manufactured by the General Dynamics Corporation, Pomona Division, later a part of Raytheon. Consisting of a radar-guided 20 mm Vulcan cannon mounted on a swiveling base, the Phalanx has been used by the United States Navy and the naval forces of 15 other countries. The US Navy deploys it on every class of surface combat ship, except the Zumwalt-class destroyer and San Antonio-class amphibious transport dock. Other users include the British Royal Navy, the Royal Australian Navy, the Royal Canadian Navy and the US Coast Guard .