I have the Belkin TuneBase FM hands-free. When I got my iPhone 4, I ordered the bumper case. As everyone found it, it does not fit into the Tunebase because the plastic around the dock connector on the iPhone doesn't let the belkin reach far enough. I took a dremel to the belkin base and chamfered (shaved) the corners of the dock area so it would fit up in the opening on the bumper. After doing that, the iPhone now fits perfect in the unit and has a very secure grip because of the rubber on the tunebase and the rubber on the bumper case. The modification is very minimal and I personally don't care that it looks a little bit less than perfect because of the added function and features. I can take a picture of it if people are interested.