Summary: Bought this for back up for my DS214+. It was easy to set up and can be an additional RAID volume or 2 additional single disk volumes. I'm not sure why some are complaining about the plastic housing.
Summary: I love all of their products. This allowed me to easily expand a client's DS710+ that had 2x4TB to 4x4TB of storage. Just plugged into the DS710+ with the provided custom eSATA cable and you are good to go. The custom eSATA cable contains thumbscrews that hold the cable SOLIDLY in place.
Summary: I have a Synology DS213+, Upgraded from an original ReadyNAS. I underestimated the storage I would need and with just the DS213+ so I purchased the 2Bay Expansion Unit. For hard drives used the WD Red 3TB, which are also in the DS213+. Hook up was easy for power and link cable to the main unit.