SIX SIZE 12 AWG CONDUCTORS ARE SPLICED IN A BOX THAT HAS NO GROUNDING WIRES, LAMPS OR DEVICES, AND HAS A FLAT COVER. WHAT IS MINIMUM GRADE SIZE ROUND OCTAGONAL BOX THAT MAY BE USED?

SIX SIZE 12 AWG CONDUCTORS ARE SPLICED IN A BOX THAT HAS NO GROUNDING WIRES, LAMPS OR DEVICES, AND HAS A FLAT COVER. WHAT IS MINIMUM GRADE SIZE ROUND OCTAGONAL BOX THAT MAY BE USED?