There are asymmetrical rubber bumpers on the back and bottom that flip over for more space if you have a cased device. They can also be removed entirely if you have a really thick case.
One of the reasons why I really like the Elevation design over other designs is they way you can change these bumpers very quickly if you regularly use the dock with different phones of different thickness's (with the 12 south stand for example, you can adjust the back, but adjusting the bottom requires you to disassemble the entire thing...)