"5.25-inch" drive: (5.75 in × 8 in × 1.63 in = 146.1 mm × 203 mm × 41.4 mm) Most desktop models of drives for optical 120-mm discs (DVD-ROM or CD-ROM drives, CD or DVD burners), are designed to be mounted into a so-called "5.25-inch slot", which obtained its nickname because this slot size was initially used by drives for 5 inches floppy disks in the IBM PC AT. (