For a single 30 to 60A receptacle. RACO surface covers are used to support switches or receptacles in areas where the box is surface mounted or positioned in exposed work applications. Size : 4" 2.625" diameter Cubic inches: 6-1/2 Used to support switches or receptacles in areas where the box is surface mounted or positioned in exposed work applications For a single 30 to 60A receptacle Conforms to new code requiring 4 wires with range and dryer applications.