The SyQuest 5.25-inch disks were removable hard-disk cartridges, initially introduced by SyQuest in 1988.
The SQ400 cartridge had a capacity of 44 MB, and the SQ800 (released in 1991) had a capacity of 88 MB. Initially, the 88 MB drives could only read and not write to 44 MB disks until a combination drive was introduced. The SQ2000 disk was introduced in 1994 and had a capacity of 200 MB.
The 5.25-inch generation of SyQuest disks were popular with Apple Macintosh owners, and used to transfer and backup large amounts of data by graphic artists, musicians and engineers.
By 1993, SyQuest had begun releasing smaller 3.5-inch form factor disks. These were popular, but because of the huge installed base of the SyQuest 5.25-inch drives, the 3.5-inch cartridges were not as successful as them.