Filler Strips provide an incredibly easy way to adjust the width of the shutter set without having to use a saw. -Each strip is 1/8" thick. To reduce the width of the set by 1/8", simply remove a Filler Strip. Each subsequent strip reduces the width by 1/8" more. -If you take off too many filler strips, simply add back as many as necessary. -Filler Strips make it easier than ever to install shutters on the inside of the window. -They can also be used for outside mounts when more depth clearance is required.