To gain access to the interior, simply loosen the thumbscrews that hold each side panel in place. The entire interior is black and of excellent quality. While the layout is quite traditional, Cooler Master included a divider for a separate PSU compartment.
On the backside, you will find around 25 mm of space to hide and route any cables. There are also two mounting possibilities for SSDs. The Mastercase 5 comes with several Velcro strips to keep the cables at bay, but a nice trench behind these will also help in really pinning them down nicely. This is possible due to the sheer width of the chassis.
The bay at the very bottom of the front may be used for a 2x HDD cage. You may move the one in the upper-most portion of the chassis down there, or buy additional ones if you have more drives. In that upper segment, you will also find the bracket for the 5.25" drives. It comes with a tool-less sliding lock for easy assembly. As has already been mentioned, you may remove all these parts to reveal the pre-installed 140 mm fan and the ability to hold a radiator of up to 420 mm in size. A cutout in the external drive bay bracket, similar to the one in the dividing plate, should also make utilizing the drive bay in the very top when installing a 360 mm radiator into the front possible. Such a setup will obviously keep you from installing any 3.5" hard-drive cages.
The PSU bay in the rear can't be accessed through the side for assembly since there is also a guiding rail on the floor. Above that are the seven expansion slots, with each of their covers held in place by a thumbscrew. The 140 mm exhaust fan in the rear can be aligned with a tower cooler for as much airflow as possible, which should maximize cooling performance nicely.
There are two SSD brackets on top of the dividing plate. Cooler Master ensured that there is enough space behind these, as well as two cable-routing holes. You may take these brackets and attach them to the backside of the motherboard tray for even more flexibility.
All the cables within the Mastercase 5 come with black sleeving to match the interior color scheme and are of the default variety. This means that you should run into no issues while connecting these to a modern motherboard.
Extra Parts Installed - Inside
As we got some extra parts for the interior to truly make the Mastercase 5 ours, we went ahead and installed them all. The dual-HDD cage was placed on the very bottom, and the triple variant fit perfectly into the top compartment. The multiple mounting holes toward the front make placing these cages at just about any height possible, so there are no limits to which hardware configurations you may pick. I can see users completely removing the external drive bracket to align two hard-drive cages in such a way as to allow for a long GPU to perfectly fit in-between.