The below left image shows the front of the device, where we see it differs from the other two by being made of plastic and not metal. Other differences here include the fact that there are now locks, and that the hinged doors are part of the housing and do not come out as part of a drive tray. On the left edge of the unit there are two USB 3.0 ports, a fan speed controller switch (high, low, auto), and a button for each drive which doubles as a light to indicate status. As delivered, the default position for these buttons is off, which means your drives will not be detected by your system until you press the button to each one on. On the back of the device we see that there are three data connectors, but just two power connectors. I think getting down to one power connector would have been ideal for cable management, but oh well. The drives in this unit are actively cooled, and the fan is (obviously) mounted externally to the housing. The two black cables coming out of the unit in the below right image are for USB 3.0. I really wish these were able to be unplugged, as I don't intend to use them and now they are just going to clutter up the inside of my case. These are fairly thick, stiff cables that are attached permanently to the housing and will require some sort of cable management to keep out of the way.
The next images show the housing from a variety of angles, and while the front is black plastic, the rest of the sides are silver colored metal.
The drive doors hinge open and provide just enough clearance to slide in three drives. There is just a little bit of space between each drive, and there is just the tiniest of openings for air to get from the drives to the fan through the PCB, so I am hoping that the airflow is sufficient for three busy drives in here! The drive bay doors have some holes in them for ventilation, but are for the most part solid - as are the sides of the unit. Just by appearances, the MB973SP-2B's design was not heavily focused on drive cooling.
In the last set of images we see three 3TB Seagate drive inserted in to the MB973SP-2B. They went in smoothly, and closing the doors made them seat properly on the internal SATA data and power connectors