The Define XL has a black and white interior where the chassis has a flat black coating and the removable hard drive trays and expansion port covers are white. The black and white color scheme is very clean and creates a very pleasant contrast within the case, and the white fans help tie the color scheme together.
The rubber grommets covering the numerous cable management holes are well made and do a good job of concealing cabling. The cable management is very easy due to the four pre-cut holes running along the length of the motherboard as well as the grommet near the power supply allowing for all power cables to be cleanly routed out the back. The space in between the motherboard and rear side panel also has a bit more depth than normal, which makes routing the main 24-pin power cable much easier than I've had in many other cases. There is also a large cable management hole near the top for easy routing of the CPU power cable.
The Define XL is divided into three "thermal chambers" as Fractal Design calls them. The first is the primary motherboard area which contains most of your components with high thermal output, such as you graphics card and processor. The front 140mm fan intakes cool external air and moves it over the removable drive bay to cool the main compartment. The second is the power supply area, which may intake from the bottom, or the lid removed from the isolating "shelf" to intake from the main chamber if you'd prefer to have your power supply fan facing upwards. The third chamber is the lower HDD cage, which is cooled by adding an additional 140mm fan to the bottom slot of the front panel.
The power supply mounting area contains rubber pillars which allow the power supply to rest in an elevated position to improve airflow through the power supply's fan, and the rubber studs allow for very good vibration absorption. The PSU mounting bracket on the back is rotatable and removable, so you may actually attach your power supply to the bracket externally, then install the bracket easily onto the back of the case in whichever orientation you'd like. The bottom intake for the power supply is filtered, as we noted before.
The drive bays all feature removable trays which enable easy mounting of your harddrives, and they include holes on the bottoms to accommodate mounting SSDs without any additional brackets. The trays then slide easily into place and the tabs snap comfortingly into position in the drive bays. The upper drive bay may be removed to enable better airflow from the top 140mm fan, and the 5.25-inch drive bay has an additional bracket for a third front fan, as seen in the bottom right image.
An interesting aspect of the Define XL is its top 180mm fan, which is at a slight angle and exhausts directly out of the back, which substantially cuts down on external noise hear in front of the case.
The motherboard tray has a large CPU retention hole which is covered by a steel door which attached with a thumb screw for tool-less removable and attachment. The hole provides alot of flexibility for different motherboard layouts so that you'll still have access to the rear mounting bracket of your CPU cooler. There are also plenty of strategically-placed mounting points for zip ties or other cable management clamps. To reiterate, there's a healthy amount of clearance on the rear side of the motherboard tray, so we were able to get our main 24-pin power connector to lay in between the side panel without forcing it to do so.
The side panels are made out of steel, and are quite heavy themselves. They swing out instead of the notch-and-slide method, which is a lifesaver given their size and weight. As you can see, the side intake vent comes out of the box covered with the sound-absorbing foam for ultra-quiet operation, but may be easily removed if you want to add additional cooling to the side. The sound-dampening material is quite dense, and also adds a considerable amount to the weight of the side panels as well.