Magnetic disk cartridge

A magnetic disk cartridge comprising:

• a magnetic disk,
• a center core supporting the center of the magnetic disk,
• a cassette shell encasing the magnetic disk to be rotatable therein and being formed in one side surface with a magnetic head access opening, the cassette shell including a first cassette shell half formed with an open portion through which the center core is exposed and a second cassette shell half mating with the first cassette shell half, wherein
• an inner surface of at least one cassette shell half lying parallel to the magnetic disk is formed with an annular recess which reduces a wall thickness of a portion of the at least one cassette shell half,
• the annular recess is formed with a step at its outer periphery and with a ring-shaped projection at a location corresponding to that of a flange portion of the center core, and
• a sheet of elastic material having a liner attached to a surface facing the magnetic disk is fixed on the at least one cassette shell half to cover the annular recess with a peripheral portion thereof fastened to the step and a center portion thereof supported by the ring-shaped projection.