The Steel City 53151234 is a new, pre-galvanized steel square box extension ring designed to increase the capacity of existing 4-inch square electrical boxes. With a depth of 1-1/2 inches and a total capacity of 21 cubic inches, it provides ample space for additional wiring or devices. The extension ring features 12 knockouts, including eight 1/2-inch and four 1/2-inch/3/4-inch eccentric knockouts, allowing for flexible conduit entry. It is UL Listed, ensuring compliance with safety and performance standards. This extension ring is ideal for both commercial and residential electrical installations requiring extra box depth. Its sturdy construction and versatile knockout configuration make it a reliable solution for a variety of wiring applications.