Specification :

Utility boxes, also called handy boxes, are used for convenience outlets, switch boxes or small junction boxes. They are popular for surface-mounted wiring. Extension rings provide a means for adding additional cubic capacity or as an outlet box for surface conduit.

Size:
4" x 2-1/ 8" x 1-1/ 2" 11.5 cu. in. interior. 4" x 2-1/ 8" x 1-7/ 8" 13.0 cu. in. interior.
4" x 2-1/ 8" x 2-1/ 8" 16.5 cu. in. interior.