This IDE HDD Adapter means that you can use two 2.5in IDE hard drives in place of a single 3.5in IDE hard drive. Simply mount two 2.5in IDE hard drives to the IDE35252X adapter & connect the mounted drives to the onboard 44-pin IDE connectors provided. The individual (44-pin) connections are then connected to the computer power supply using a single 40-pin IDE power connection. This convenient IDE storage adapter also allows users to designate the installed 2.5in drives to operate as either a master or slave drive, & provides a drive activity LED indicator for easy monitoring.