The Javelin was a water-based vehicle equipped with missiles designed to strike aerial vehicles like airspeeders and starships in the sky. The Rebel Alliance employed these crafts to protect their water fleets and transport ships from aerial attacks, as well as to defend Rebel shipbuilding facilities from air raids.
The Heavy Javelin represented an advancement over the original Javelin design. The primary enhancement was the doubling of surface-to-air missile launchers; it possessed two instead of the original's single launcher.