The SA8.5-GRILLE-R-RF 8.5" Round Retrofit Trim Kit is designed to solve two installation needs. First, when installing an SA853 model in a dropped ceiling, it is impossible to provide a clean visual cut in the ceiling board. The retrofit kit provides a 3/8" edge to cover the edge of the ceiling board, covering any rough-cut issues. This is very similar to a retrofit speaker that has a flange to cover the cutout edge made in sheetrock, like our older FX Series.
Second, the retrofit trim kit can be used to cover any errors made in a solid surface cutout where a wood ceiling panel was not cut exactly or there was tear-out and the visual would not be appealing.