PURPOSE: To make the cartridge unloadable to a drive device whose specification is different and to prevent the occurrence of a lifting phenomenon of an upper half member.

CONSTITUTION: A cartridge main body 2 is constituted by combining the upper half member 3 molded out of a synthetic resin material and a base plate 4 formed with a metal plate, while an identification projecting part 27 for identifying specifications of a magnetic tape 7 is provided in the side surface part 3C of the cartridge main body 2, facing an inserting guide recessed part 26 to be engaged with an inserting guide projecting part formed in a cartridge inserting opening on the side of a drive device. A means 45 for combining the base plate 4 is formed on the upper half member 3 in contiguity with this identification projecting part 27.