GPSMAP 421 ChartplotterFeatures an ultra-bright 4" 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 position at sea. They are ready to go with a built-in, satellite-enhanced worldwide basemap and Garmin's proven easy-t0-use interface designed to help you navigate the open waters with ease. Both models are compatible with various NMEA 2000 components, inculuding Garmin's full lineup of NMEA 2000 marine sensors and autopilots.Features and Specifications:Ultra-bright 4" diagonal QVGA display, 240 x 320 pixels - over 800 nits of brightnessNMEA 2000 certified for seamless integration with the Garmin marine lineupPreloaded worldwide marine basemapCompatible with GXM 51 for XM Satellite Radio and XM WX Satellite WeatherHigh-speed processor for fast screen redraws and smooth panningStreamlined 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 a 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: 5.0"H x 5.7"W x 2.7"D (12.7cm H x 14.5cm W x 6.9cm D)