Type cv brackets allow box to be mounted to flat side of metal or wood studs 1/2" and 3/4" e.k.o..
From the Manufacturer
The Steel City 52171 CV 1/2 3/4 is a pre-galvanized steel square box with an CV- bracket and 1/2-Inch and 3/4-Inch eccentric knockouts. Is a 4-Inch box that is 2-1/8-Inch deep with a 30.3-Cubic Inch capacity and is intended for use with non-metallic sheathed cable. On each side and on both ends of the box there are two 1/2-Inch knockouts and one 1/2-Inch and 3/4-Inch eccentric knockout. The bottom of the box contains three 1/2-Inch knockout and two 1/2-Inch and 3/4-Inch eccentric knockouts. The knockouts provide better contact with the conduit fitting and locknut to the box while improving the grounding path. The individual wedges on an eccentric knockout can be removed without going all the way around the circle to either be a 1/2-Inch or 3/4-Inch. The patented CV-bracket design mounts the box to the flat side of metal or wood studs. Steel City is the industries leading product line of metallic switch and outlet boxes used in electrical construction. Since 1904, its products have represented the highest quality standards in manufacturing and innovative design, with one of the most complete offerings available.