Abstract: A cartridge assembly (10) for holding disks or similar substrates includes a cassette (12) provided with a plurality of curved grooved channels (20) of substantially even channel width and at least one protruding feature (34. 36. 40) into each channel (20) for reducing the channel width, the protruding features (34, 36, 40) being provided as areas of greater channel wall thickness. The protrusions allow more compact storage of disks within the cartridge (10) while still ensuring that the disks do not touch one another during transportation and handling. One or more burrs (44) are also provided in each channel (20) to prevent or reduce disk spin during transportation of the cartridge (10).