The RT-AC66U has a simple look with a striped black pattern on top, and is surprisingly thin.
The back of the RT-AC66U fits quite a lot into a small space as it features 3 x Antenna screws, as well as 2 x USB 2.0 ports and the 5 xRJ45 Gigabit ports.
On the front of the device are a series of LED's, in fact an impressive 9 blue LED's. These will, at a glance, tell you exactly what's plugged in to the RT-AC66U and if any problems have arisen.
After fitting the antennas, the RT-AC66U takes up quite a bit more space, however it should give excellent coverage.
From the back it does look a bit cramped, but none of the ports are blocked with the Antennas in the standard and recommended arrangement.