On the front of the case is an all aluminum bezel, and offers a unique curved design. A door on the top half covers four 5.25" drive bays, two 3.5" bays, as well as the power and reset switches. Below this front panel door is a 120mm intake fan with blue LEDs. On the top of the chassis is the USB, IEEE-1394 Firewire, and audio ports. On the side panel is an 80mm intake fan slot with an optional attachment of a CPU air duct. Below that is a rectangular area of holes, which does not have mounts for any fans, but will allow some airflow to the expansion slot area. The side panel comes equipped with a handle for easy removal/installation. At the rear of the chassis are two rubber grommets for water-cooling if you will be using an external radiator. Alternatively, you could use these two holes for sending out any cables or other wires that you might have. At the rear is also a fan mount that supports 80, 92, and 120mm fans. The Mystique 631 comes preinstalled with a 120mm Cooler Master fan.
Looking inside the Cooler Master Mystique 631, at the front are the four external 5.25" drive bays, two external 3.5" drive bays, and four internal 3.5" drive bays. The mounting procedure for drives in these bays are straight forward, and do not really differentiate from the tool-less mounting on other cases. The internal 3.5" drive bays are placed directly in front of the 120mm intake fan. The Mystique 631 supports ATX and micro ATX motherboards. Another tool-less feature to this case is the expansion slot area. The inside of this case is very well laid out, and is quite spacious for its size.