Steel City 54151CFB-BHL-OW Pre-Galvanized Steel Octagon Ceiling Fan Support Box with Old Work Bar Hanger and 1/2-Inch Knockouts Bar is expandable 16-Inch to 24-Inch 16-Inch span the bar can hold 70-Pound fans and 200-Pound fixtures 24-Inch span the bar can hold 35-Pound fans and 50-Pound fixtures For use with non-metallic sheathed cable UL listed