Serves a purpose of boardering out Faux Tin Ceiling Tiles of your choice.  The Reason some people use the these fillers is because they don't want to cut the design of their tiles and so they use the Faux Tin Filler arround the perimeter of the ceiling.   Fillers cannot always be used, especially when the room is not asymmetrical, because the filler would be a different size in many places. On the other hand if you have nice square or rectangular room a filler can make the project look more finished and professional.  Make sure to use the same colors for tiles and the filler.