The Disk System's Disk Cards are somewhat proprietary 71 mm × 76 mm (2.8 × 3 in) 56K-per-side double-sided floppy. They are a slight modification of Mitsumi's Quick Disk 71 mm 2.8 in square disk format which is used in a handful of Japanese computers and various synthesizer keyboards, along with a few word processors. QuickDisk drives are in a few devices in Europe and North America. Mitsumi already had close relations with Nintendo, as it manufactured the Famicom and NES consoles, and possibly other Nintendo hardware.
