Additional Details ------------------------------ Product description: Molded of engineering grade non-metallic thermoplastic. Adjustable, no need to remove or relocate mounting screws to re-position the box. Slots retain slider plate and guide it in a straight motion. Internal rails guide slider plate for smooth mounting adjustability in wall substrates from 1/2 in to 1-3/8 in thick and ceiling substrates from 1/2 in to 1-5/32 in. Square corner design allows easy wall cut-in (Old work applications). Molded spline device holes for quick device screw installation. 42 cu-in volume, two 1/2 in knockouts. Internal steel, stud/wood screws. 3-9/16 in D x 4 in W x 3-3/4 in H. UL listed for 2 hrs fire resistive walls.