Included within a computer case to place disk drives such as hard and floppy disk drives and devices such as CD-ROM's and DVD-ROM's. There are usually two types of drive bays included in a computer case, which are 3.5 inch and 5.25 inch (3.5 inch - floppy drives , 5.25 inch - hard disks). Obviously the bigger the computer case the more drive bays and devices can be added.