Steel City 52151-1/2-3/4 Galvanized Steel Square Box with 1/2-Inch and 3/4-Inch Knockouts, FULL BOX OF 30 The Steel City 52151-1/2 3/4 is a pre-galvanized steel square box with 1/2-Inch and 3/4-Inch conduit knockouts. Is a 4-Inch box that is 1-1/2-Inch deep with a 21-Cubic Inch capacity and is intended for use with conduits. On each side an both ends of the box there are two 1/2-Inch and one 3/4-Inch conduit knockouts while the bottom has three 1/2-Inch and two 3/4-Inch conduit knockouts. The knockouts provide better contact with the conduit fitting and locknut to the box while improving the grounding path. The box protects the device from damage and gives access to the wiring even after the construction is complete. 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. Drawn Construction For use with conduits 21-Cubic Inch capacity Protects device from damage UL listed