Constructed of sturdy steel with a corrosion proof powder coating, these brackets are designed to mount filter housings as part of a 3-Stage or 4-Stage RO System Undersink RO System, or as standalone water filters. ** The mounting bracket has universal pre-drilled holes for wall anchorings, and as well as holes for screws to mount the top of the filter housings and mounting clips, as well as openings for pressure relief buttons.