Drive bay

Full-height, 2 half-height, and 3.5" drives

A drive bay is a standardized-sized area for adding hardware to a computer. Most drive bays are used to store drives, although they can also be used for front-end USB ports, I/O bays, tool storage, and other uses.

When installing a drive in a bay, it usually must be secured in place in a drive holder with several screws, and then secured into the bay itself with more screws. Then, any necessary power, data transfer, and other cables are routed into and connected into the drive.

Over the years since the introduction of the IBM PC, it has had three types of drive bay, of which two are in common use today.

Full-height bays were found in old PCs in the early to mid-1980's. They were approximately 3.5" high by 5.75" wide, and used mainly for hard disks and floppy disk drives.

Half-height or "5.25" drive bays are approximately 1.75" high by 5.75" wide, and are the standard housing for CD and DVD drives in modern computers, but are sometimes used for other things. They used to be called half-height in reference to full-height bays, and are now better-known as 5.25" in comparison with 3.5" bays. It is important to note that the name does not refer to the width of the bay itself, but rather to the width of the disks used by the floppy drives which mounted in these bays.

"3.5"" bays, like their larger counterparts, are named for diskette dimensions; their actual width is about 4 inches. Those with an opening in the front of the case are generally used for floppy or Zip drives. Hard drives in modern computers are typically mounted in fully internal 4"(nominally 3.5") bays. Of course, nowadays most computers don't come with floppy drives at all since CD/DVD-RW drives are very common.