Unlike standard ISO or CDI files (which are compressed or stripped to fit on a CD-R), a is a 1:1 raw dump of the original Sega Dreamcast GD-ROM.

is a classic arcade football (soccer) game developed by Sega AM2 and released in 1997. The "gdizip" keyword refers to the GDI file format —a raw disc image of a Sega Dreamcast GD-ROM—compressed into a ZIP archive for use with modern emulators or original hardware mods. Understanding the "GDIZIP" format