the 5- 1/4" came in 160K, 180K, 360K and 1.2MB (I think I missed one (720K?)); 3-1/2 came in 720K, 1.44MB, and later on, 2.88MB. the 2.88MB drives are rare because when they were released the floppy drive was already falling out of favour as the main way of saving files and backups, additionally, the fact that the drive used perpendicular recording made the drives themselves expensive enough to not be a commodity, which means they were included only on a few machines.