The ISS Brackets are made with extruded aluminum in a clear anodized finish. The size of the shelf determines which bracket size to use. The actual bracket length is shorter than the shelf size by 3/4" to provide the look of the ISS Bracket when facing forward. Also a 12" ISS bracket with a 12" deep shelf will not touch the wall when rear facing on a pole mounted application. Therefore, the usable length of a 12" bracket is 11 1/4".