This is the Black X from Thermaltake.
This is a device that allows you to take an internal hard drive (inserted in the top in the photo) and have your computer read that externally. We use this as a part of our back-up process as our way of getting images off-site for cheap. What we do, is we get home from shooting a gig, then download our RAW images to multiple hard drives with this being one of them. We then take this hard drive out of the Black X, put it back in the blue static bag that it came with (static can mess up hard drives when they are exposed) and then send the RAW images on the drive over to a friends house.
This allows us to have an off-site back up in case of flood, fire or theft, and protects our clients images as best we can. We highly recommend doing that especially if you shoot weddings which can’t be re-shot.
The Black X is only $50, and then you can buy one internal hard drive for around $69 or so, then just erase it when you need to once your JPG images from the shoot edited and backed up online. For $119 total you can have an off-site back up system that works great!