scope:

This International Standard specifies the characteristics of 90 mm flexible disk cartridges of 21 MB formatted capacity, recorded at 31 831 ftprad in the Inner zone and 47 747 ftprad in the Outer zone with sector servo tracking on 326 tracks on each side, using 2-7 RLL recording. Such flexible disk cartridges are identified as ISO Type 305. It specifies the mechanical, physical and magnetic characteristics of the cartridge, so as to provide physical interchangeability between data processing systems.