Our stackable top hat is heavy gauge steel contructed, which protects rear side of speakers from dirt, debris, or other disturbances. It can be used for a back box in ceilings and walls. It has an undercoating that eliminates any mechanical or acoustical resonance caused by vibration. It has rust preventative finish four combination knockouts. It includes 4 J-clips for screw mounting of baffles and perforated mounting straps for 8 inch speaker combinations.