The form factor describes the size, shape, and physical arrangement of computer components such as motherboards, add on cards, power supplies, disk drives and so on. The physical size of a device as measured by outside dimensions. With regard to a disk drive, the form factor is the overall diameter of the platters and case, such as 3.5in or 5.25in, not the size in terms of storage capacity. If the drive is a 5.25in form factor it means that the drive is the same size as a 5.25in diskette drive and uses the same fixing points.
