Rear View Part number 3500525,3500533 The illustration to the left is the back of the tower case. There are several hyperlinks on the back of the tower that provide a closer view of the individual components. Listed are just some of the major components. Many more views are available by browsing the graphic and clicking the hyperlinks it offers. Closerview of the power supply I/O ports USB port Secondary fan Expansion slots Keyboard and mouse connectors