X-DUO Dual-Bay Docking USB 3.0 is not only a HDD device for your PC, it also works as a standalone HDD duplicator or HDD cleaner. It is designed to fit the latest 2.5" and 3.5" SATA HDDs. The USB 3.0 Interface makes this unit hot-swappable plug and play and it is downward compatible to USB 2.0 and USB 1.1 USB HDD Device: 2 HDDs can be installed in the X-DUO to work as a standard hard drive dock, which connected to the computer. HDD DUPLICATOR: Duplicates the contents of Hard drive 1 (HDD1) to Hard drive 2 (HDD2), sector by sector. The capacity of HDD2 must be larger than HDD1. The remaining spare capacity in the 2nd hard drive becomes a spare partition. HDD ERASE: Erases all information stored on the hard drives. It destroys all of the HDDs data, sector by sector. If you are recycling your computer or have a disk that you no longer need, you can wipe it clean with the erase function, safe in the knowledge that your data cannot be re-created. X-Duo Dual-Bay Docking USB 3.0 is excellent for home and small business use. The stand alone function for disk duplication saves time and reduces complexitey in duplicating disks.