Hubbell's GFCI receptacles can be mounted on any standard 2.50" (63.5) deep box. A feed-thru feature provides protection not only at that receptacle but also at any other receptacle located downstream from it on the same circuit. These devices meet the requirements of The National Electric Code (NEC) and American Boat and Yacht Council Standard and will accept locking fork terminals.Caution: Ground Fault Receptacles should not be mounted in locations exposed to salt spray nor in the engine room. For GFCI protection of such locations, downstream feeding from an internally located Ground Fault Receptacle is recommended.