Abstract: A cassette assembly for holding circular and non-circular disks is provided. A cassette body has a top wall, a bottom wall, opposite side walls, and an open front, creating an inside and outside of the cassette body. The side walls have grooves adapted to receive and hold the disk. One or more first stops are provided inside the cassette body adjacent the grooves for stopping non-circular disks at a location in the grooves as the non-circular disks are placed in the grooves from the front. Additionally, one or more removable second stops inside the cassette body are spaced inwardly from the first stops for stopping the circular disks at the location in the groove as the circular disks are placed in the grooves from the front, so that the geometric center of the circular disk approximately aligns with the geometric center of the non-circular disk.