Garmin GPSMAP 520s Dual Frequency Combo - Internal Antenna Ultra-bright 5" diagonal QVGA display, 320 x 240 pixels 800 nits of brightness New streamlined user interface offers easy selection of functions and features Preloaded worldwide satellite imagery Single SD memory card slot for BlueChart g2 Vision cards, as well as saving waypoints, routes and tracks to a SD card which can be shared with others Built-in GPS antenna BNC connector for optional GA29 remote GPS antenna Backlit keypad for easier operation at night Two NMEA0183 I/O ports Unit dimensions: 6.4" W x 5.9" H x 2.9" D Sounder Features: New sounder design featuring excellent shallow water performance Power output: 500 watts (RMS) 4000 watts (peak to peak), dual frequency Depth: 1,500 feet (dual frequency), 900 feet (dual beam) Choose dual frequency transducer 50kHz (45°), 200kHz (10°) for maximum saltwater performance Patented transom/trolling mount transducer UltraScroll™ high rep rate sonar provides lightning-fast screen updates New AutoGain technology enhances target visibility CANet™ proprietary bus allows display and control of full feature sounder data on 2nd Garmin chartplotter See-Thru® technology: shows weak and strong returns simultaneously Water temperature log graphically records water temp data A-scope (in dual frequency mode) Whiteline Adjustable depth line helps gauge desired fishing levels and bottom clearance Split zoom display offers a closer look at fish targets and bottom structure 2X, 4X and bottomlock zoom Adjustable keel offset Alarms for fish size, shallow water, deep water and low battery