Typically the thick part goes in the back, but in my experience you can play around with the pad angle For my pair of 400i's I ended up placing the thicker part of the angled pads in the front to tamp down some of the treble. It worked great. Think about it. The angle of the pads is trying to better match you ear angle. This improves the coupling efficiency to the parts of the ear, but if it isn't correct for your ears there may be other angles that are better. Play with the pad angles if you want. Nothing wrong with that.