Mostly cosmetic, just hides the guts of the sunroof tracks. My 08 did not even have anything, just exposed sunroof parts. The "bellows" on the 14 are kind of crap, the one on my drivers side kept falling off, so I just super glued it back into place. The same item on my 16 is a much better item, it is larger, so it covers more of the working parts, and fits a lot better. See if they can replace the pieces with the newer versions, overall better piece.