GPSMAP 531 ChartplotterFeatures a large ultra-bright 5" QVGA display along with an improved high-speed digital design for faster map drawing and panning speeds Plus, these waterproof units have a high-sensitivity internal GPS receiver, so mariners will always know their opsition on the water. They are ready to go with built-in cartography for inland U.S. waters (over 14,000 lakes) and Garmin's proven easy-to-use interface designed to help you navigate the waters with ease.Features and Specifications:Large, ultra-bright 5" diagonal QVGA display, 234 x 320 pixels - over 800 nits of brightnessPreloaded with charts for over 14,000 U.S. lakes and navigable riversCompatible with GXM 51 for XM Satellite Radio and XM WX Satellite WeatherBuilt-in high-sensitivity GPS receiverHigh-speed processor for fast screen redraws and smooth panningTwo NMEA 0183 I/O portsStreamlined user interface makes it simple to select modes and featuresSingle SD memory card slot for BlueChart g2 Vision cards, as well as saving waypoints, routes and tracks to an SD cardOptional BlueChart g2 Vision cards provide marine chart detail and enhanced navigation features like Auto Guidance, satellite imagery, 3-D Mariner's Eye View and 3-D Fish Eye ViewBacklit keypad for easy operation in low light conditionsUnit dimensions: 5.9"H x6.4"W x 2.9"D