GPSMAP 431S Chartplotter Combo - Includes Dual Beam TransducerFeatures 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 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:Ultra-bright 4" diagonal QVGA display, 240 x 320 pixels - over 800 nits of brightnessPreloaded with charts for over 14,000 U.S. lakes and navigable riversBuilt-in high-sensitivity GPS receiverHigh-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 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: 5.0"H x 5.7"W x 2.7"DPower output: 400 watts (RMS) 3200 watts (peak to peak), dual beamDepth: 900 feet/300 meters (dual beam)Use a dual frequency transducer 80 kHz (45 degrees), 200kHz (14 degrees) for maximum saltwater performanceUltraScroll high rep rate sonar provides lightning-fast screen updatesAutoGain technology enhances target visibilitySee-Thru technology shows weak and strong returns simultaneouslyWater temperature log graphically records water temp dataA-scopeRound flasher display modeWhitelineAdjustable depth line helps gauge desired fishing levels and bottom clearanceSplit zoom display offers a closer look at fish targets and bottom structure2X, 4X, and bottomlock zoomAdjustable keel offsetAlarms for fish size, shallow water, deep water, and low battery