Product details:

PVC, single gang 21 cu. in. Adjusta Box with bracket for metal or wood studs allows for adjustment of the box to the wall surface by turning a screw on the metal bracket. Mounts square and secure everytime. Comes preset at 1/2"". four 1/2"" knockouts. UL listed. No. B121ADJ: Box Type: Adjustable, Number Of Gangs: 1 Gang, Material: PVC, Cubic Capacity: 21 cu in, Mounting Type: Metal Bracket, Knockouts: (4) 1/2"".