A large mechanical VTOL multipurpose fighter
The GUN R-1/A Flying Dog is a VTOL multipurpose fighter armed with a 22 mm gatling gun, 2 medium range advanced warhead launchers and a 200 mm beam cannon, protected with depleted uranium armor and powered by 7 GUN turbofan engines (11,000 lbs of thrust per engine). This boss is fought after playing Security Hall.
According to Sonic X, it is 3.6 meters in both height and width, and weighs 5.4 tons. There is also an unseen two seater version that presumably looks much like the standard version but the technical data is the same.