The Fan Master Jr. non-metallic support box allows you to safely attach a lighting fixture or ceiling fan to a building's structural support, so the ceiling fan is supported by the joist, not the box. The Fan Master Jr. design provides additional wiring space in one place, on the side, so all of the fan or fixture wiring will fit inside the box without having to split wires due to limited space. You can install the Fan Master Jr. on standard joists as well as wider joist configurations where a saddle style box will not fit. Perfect for new construction, the Fan Master Jr. can be used in applications where duct work or wiring is present. UL listed for fixture support of 150 pounds or less and fan support of 70 pounds or less. Fan Master Jr. has a two-hour fire rating.