53151 - 4 in. square extension ring 21.0 cu in. 1-1/2 in. deep

4 in. square extension ring, 1-1/2 in. deep, 21.0 cubic in. Concentric knockouts. To extend an existing 4 in. square box Mount with screws directly on the original box Made of Steel Cubic capacity: 21.0 cu. in. 1-1/2 in. deep Adds volume