Floppy Disk, 5-1/4" 5.25-inch floppy disks are a magnetic data storage format with a flat circular plastic disk that has a magnetic coating (similar to magnetic tapes) inside a protective sleeve.  IBM released an 8-inch (203 x 203 x 1.6mm) flexible disk in 1972 which could store 80Kbytes of data.  ITC (Verbatim) commercialized a flexible 5.25-inch (133.3 x 133.3 x 1.6mm) floppy disk in 1978 that could store 160Kbytes, 360Kbytes, and then 1.2Mbytes by 1994.  There were other magnetic disk formats.  Sony discontinued floppy diskette production in 2011.