Allied Moulded Products SB-CB Polycarbonate Ceiling Fixture Support Box 4 Inch x 2-3/4 Inch 25 Cubic-Inch Sliderbox Allied Moulded Products Sliderbox 4-Inch Dia Round ceiling fixture support box in beige/tan color, has polycarbonate construction. It measures 4 Inch x 2-3/4 Inch. Box featuring machine tapped fixture holes, has internal steel stud/wood screws with adjustable slider plate for additional substrate thickness. It has cubic capacity of 25 Cubic-Inch. Box with two 1/2-Inch knockout is suitable for use with non-metallic sheathed cable. It comes with galvanized steel brackets, plated carbon steel New and old work residential construction 2 HR fire resistive floors and ceilings Has maximum capacity of 25 Cubic-Inch