In earthquake prone areas, there are many system requirements that a sprinkler contractor must consider. And, there are often many solutions to various seismic requirements, such as the use of flex drops, swing joints, earthquake bracing , etc. One solution used in certain scenarios is to leave a one inch annular space (i.e. a larger hole) around the sprinkler to allow it to move in an earthquake. Viking's expansion plate enables a clean, professional installation when this strategy is used. Expansion plates have a 5" (127 mm) or 5-5/16" (135 mm) outside diameter, and are available in either polished chrome or white. Custom finishes are also available upon request.