: Many North American versions of this cart actually contain a Famicom board inside with a pin adapter, making them a "Famicom-in-NES" hybrid.

fitted with a 72-pin adapter to work on Western NES consoles. Menu Systems

Often listed at #18 (likely what your query "Rom 18" refers to), a Konami shooter where you pilot a WWII-era plane.

These cartridges were technical marvels of the "gray market" industry. Some North American versions were actually Famicom (Japanese) boards

Are you trying to identify a that appears as number 18?