Think Retro: Who else kinda misses their Zip disks?:

The humble Zip disk, then, was a kind of de facto successor to the ubiquitous high-density 3.5-inch floppy. You had to buy a special drive to mount it in, because although they had about the same footprint as a regular floppy disk, they were much thicker. In fact, Zip disks had a lovely chunky, seemingly hugely robust quality compared to normal floppies.