53171 - 4 in. square extension ring 30.0 cu in. , 2-1/8 in. deep

4 in. square extension ring, 2-1/8 in. deep, 30.0 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: 30.0 cu. in. 2-1/8 in. deep Adds volume