This Westinghouse Lighting Fan Master Jr. 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. Perfect for new construction, the Fan Master Jr. can be used in applications where duct work or wiring is present. Featuring a 13-3/8-cubic-inch capacity, the box works with any model of ceiling fan. It includes two knockouts for conduit or Romex, one Romex connector, and one Romex clamp. The Fan Master Jr. is UL listed for fixture support of 150 pounds or less and fan support of 70 pounds or less on 16- and 24-inch centers (fixture support of 50 pounds or less on 24-inch centers). It has a two-hour fire rating. This case includes 12 bulk-packed Fan Master Jr.s. Each one measures 4 in high by 1/2 in deep.