These Filler Plates are designed to be used with an 18 or 24" rack running a smaller than 18" accessory panel. They are 6" in or 12" height, so if you are running a 6" panel on an 18" rack you'll want the 12" filler plates per upright, or if you are running a 12" panel you'll want a 6" filler plate per upright.
These plates are design...