CE-53151-K SQ EXTENSION
4 inches square box extension ring 4 inches height x 4 inches width x 1-1/2 inches depth 21 cubic inches and concentric knockouts.
CE-53171-K SQ EXTENSION
4 inches square box extension ring 4 inches height x 4 inches width x 2-1/8 inches depth 30 cubic inches and concentric knockouts.