The Atari XF521 was a 5.25" floppy disk drive announced at the Consumer Electronics Show (CES) in January 1985. It featured the XE series like design (gray, angular styling) and was intended as an updated, more stylish version of the popular Atari 1050 drive with true dual-density support, but it actually remained in the prototype stage and never entered mass production, giving way to the XF551.