The Wikipedia snippet below is not backed by a reliable source. Can you find one?
Click I got this! to go to Wikipedia and fix the snippet, or Next! to see another one. Good luck!
In page Floppy disk:
"Single-sided disks were coated on both sides, despite the availability of more expensive double sided disks. The reason usually given for the higher price was that double sided disks were certified error-free on both sides of the media. Double-sided disks could be used in some drives for single-sided disks, as long as an index signal was not needed. This was done one side at a time, by turning them over (flippy disks); more expensive dual-head drives which could read both sides without turning over were later produced, and eventually became used universally.[citation needed]