I keep a 2GB card in mine for screen shots and storing my *.usr file (waypoints). I also periodically copy the *.usr file to my computer so I have 2 backups of my waypoint file. As I mark new waypoints I can copy the updated file in the unit to the card so my backup is current. I had a map card in my old Lowrance and could store the waypoint file on the map card. There is usually enough room left on them to do this but I don't know if you can with the new ones. Of course you have to be careful you don't delete the map file.