Mediasonic ProBox 4 Bay Dock for 2.5' / 3.5' SATA HDD - USB 3.0 SuperSpeed & eSATA (HFD1-SU3S2) Changing HDDs frequently? Getting tired of running up and down for replacing HDDs in your old hdd enclosure? Mediasonic is now providing you a better solution for your need. Mediasonic HFD1-SU3S2 is a sleek looking design 4 bay docking station which allows you to install 2.5' or 3.5' hard disk drives and move files between your HDDs. It also has Smart Power Sync function for power saving when host computer turns off or standby.