A caddy or a mounting kit is the framework that holds the hard drive inside the notebook. Bare hard drive are not normally secured to the notebook or laptop to hold it in place. A metal or plastic device of some kind (caddy) is secured to the hard drive or in some cases totally encases the hard drive. The caddy is therefore the anchor that holds the hard drive in the notebook computer. In most notebooks or laptops the hard drive mounting pattern, generally eight screw holes, four on the bottom and two on each side, are used to hold the hard drive on or in the caddy. Hard drives made prior to 1998 may have had three screw holes on the sides and two of them were no more than 1 1/2 inches apart. All of the hard drive manufactures agreed on a new mounting hole pattern for 1998 and newer hard drives. This new pattern places the screw holes to within 1/2 inch of each end of the drive, long wise. This pattern places the mounting screw pattern 3 inches apart, long wise. So for laptop/notebook computers made after 1998, you can reuse the hard drive mounting kit or caddy comes with the computer when you upgrade hard drive. But notebook and laptop computer made prior to 1998 may require a new caddy or mounting kit when upgrading to hard drive manufactured in 1998 or later. All of the new caddies or mounting kits are built to accommodate the new mounting hole pattern.
