I could see 2 map cards as an option for someone who happens to fish different lakes on different region Navionics cards....they could insert both region map cards and then change the setting to the card they wanted to view...

Or a person that like some aspects of their Navionics card and some aspects of their Lakemaster card...they could insert both cards and then change the setting to the card they wanted to view at the time...

Rickie