 In the context of magnetic tape, the term "cassette" or "cartridge" means a length of magnetic tape in a plastic enclosure with one or two reels for controlling the motion of the tape.The type of packaging is a large determinant of the load and unload times as well as the length of tape that can be held.In a single reel cartridge there is a takeup reel in the drive while a dual reel cartridge has both takeup and supply reels in the cartridge.