The spoiler has provisions to be glued to the glass as well. At least the spoiler I got had to be glued to both the metal and the glass. As far as I know my spoiler was genuine spoiler from the aero kit, so your spoiler should be the same. The removal means that the glue must be scraped from the metal (which means it should be painted at the points of contact) as well as from the glass (with no harm)