Product review (5 stars): Perfect for 2 wall heaters that I wanted to cover up!
I bought this for my apartment electric wall heater that I don't use and wanted to hide the ugly vent and add a bit of sound proofing.  This package covered up both the one in the living room and in the bedroom and they cling just fine.  However, if heat is used, it will fall off after a few days and lose the ability to stick.  The apartment custodian apparently turned it on to see if it worked and didn't turn it off completely! After a week, it fell off and I had to replace it.  I don't have air conditioning so I have no idea how it would work with any kind of air pushing on it.  I didn't need to paint it, but it is nice to see you can paint it to match or even add wallpaper.  Some of the other reviewers came up with a clever idea to put it inside the vent covers and refasten it with the screws.  Pretty clever idea.