The mounting brackets included with the AirPort Extreme and AirPort Base Stations are not interchangeable. The top hook on the mounting bracket (815-6532) for the AirPort Base Station (Dual Ethernet) is shorter than the top hook used on the bracket (815-3263) of the earlier AirPort Base Station (Graphite).
Figure 1 AirPort Base Station mounting brackets
The AirPort Extreme Base Station bracket (815-7118) has two hooks at the top and the cable routing chamber is approximately 5 mm (3/16-in.) deeper. The deeper cable chamber allows for the routing of the additional printer and antenna cables.
Figure 2 AirPort Extreme Base Station mounting brackets