SATA Power and Data Cable - Dismantled for reference and curiosity
The XBOX 360 Hard Drive Transfer Cable connects to the XBOX 360 via one of the console's USB ports. The other end of the cable is connected to the hard drive caddy port for the new hard drive.
The existing hard drive remains in its caddy connected to the XBOX 360 and a copy of it is made via USB to the new drive. Once complete the drives and their caddies are simply swapped.
The unit is esentially a USB to SATA bridge that allows users to transfer data from one XBOX 360 drive to another; eg. during a drive capacity upgrade.
The focus of the cable is to keep in line with Microsoft's keep it simple for users theme rather than having customers remove the drive from the caddy and use a standard connector.
As of 2013, the cable could be purchased from Microsoft direct for around $20 USD.