When using MapInstall or MapSource to send mapping to a device, each map item selected is called a map segment or a map set. You can select multiple map segments and send them all at once to a device or a memory card.
Although other devices have a limit to the number of total map segments they can read, automotive devices do not. When sending maps to an automotive device, you are only limited by the following:
1 Some devices will not be able to read a file that is larger than 2GBs but are able to read an SD card larger than 2GBs. Devices that cannot read a map file larger than 2GB are the nuvi 300, 600 series, 5000, and the Streetpilot c500 series.
2 Currently MapSource and MapInstall will only allow you to send a maximum of 4GB of map data at a time. This means that although there is no limit to the number of map segments a device can receive or read, you may still only send up to 4GB of data at any one time.