A videocassette is a cartridge containing videotape. In 1969, Sony introduced a prototype for the first widespread video cassette, the ¾ʺ (1.905 cm) composite U-matic system, which Sony introduced commercially in September 1971 after working out industry standards with other manufacturers. Sony later refined it to "Broadcast Video U-matic" or BVU. Sony continued its hold on the professional market with its ever-expanding ½ʺ (1.27 cm) component video Betacam family (introduced in 1982), which, in its digital variants, is still among the professional market leaders. Panasonic had some limited success with its MII system, but never could compare to Betacam in terms of market share.