The SYSTEM 21 is a complete, blind mount loudspeaker system for hard ceiling applications. It consists of an 8C10PAX - 8" O.D. dual cone loudspeaker with a 10 oz. magnet and a TBLU - 5W-25/70V transformer. Loudspeaker and transformer are mounted on a BR8W - round, steel, screw mount baffle along with an ERD8U - 275 CID, round, steel back box.