Single Gang, Old Work Box, 20 CUIN, 4-1/8″ x 2-5/16″ x 3-5/8″ Deep, For Large Wiring Devices, Extra Wire Capacity, Lightweight, High Impact PVC Construction, For Use in Existing Construction Remodeling Work box Fits Into Standard 2″ x 4″ Constructed Wall, UL Listed For Fire Resistance. Designed for use with nonmetallic sheathed cable. Carlon(TM) Zip Box(TM) Blue boxes make fast work of any residential or light commercial application. The contractor’s choice for easy installation.