Steel City 25151 1/2 Extension Rings

It adds 11.8 cubic inches of volume. That is the number you add to the existing box capacity when you run the NEC box fill calculation, so it is the usual fix when an existing round box is overcrowded after adding conductors or a device.

Four knockouts are provided on the 25151 1/2 ring, so you can bring additional raceway or cable into the extended box without disturbing the original box entries. It is also rated for one outlet.

Steel construction with a silver (galvanized-appearance) finish, and it carries UL file E2969. Steel rings are what inspectors expect on metallic box systems where the ring has to maintain the equipment grounding path through the box.

An extension ring bolts onto the front of an existing box to add depth and volume, which is the practical answer when a box is already set in finished plaster, concrete, or drywall and cannot be pulled. The 25151 1/2 adds 11.8 cubic inches and 1-1/2 inches of depth on a 3-1/2 inch round pattern. If the box is accessible before finishes and you simply need more room, a deeper box is the cleaner install; if the wall or ceiling is closed, the ring saves the demolition.

Adding the 25151 1/2 raises the box face 1-1/2 inches toward the finished surface, so it is sized to bring a recessed round box flush with new drywall or a furred-down ceiling and to gain wiring room behind a fixture canopy. Measure from the existing box face to the finished surface first: the ring's depth is fixed at 1-1/2 inches, so if the box sits deeper than that you will need a deeper ring or a second one.