Garmin GPSmap 531 Series GPS Receiver: * Large, ultra-bright 5" diagonal QVGA display * 234 x 320 pixels * Preloaded with charts for over 14,000 US lakes and navigable rivers * Built-in high-sensitivity GPS receiver * 2 NMEA 0183 i/o ports * Streamlined user interface makes it simple to select modes and features * SD card slot * Dimensions: 5.9" x 6.4" x 2.9"