GPSMAP 392 3x4-inch Waterproof Marine GPS and Chartplotter With Sounder Product Type - GPS - CCFL backlight for display and keypad - Ultra-dim backlight for nighttime operation with user-programmable levels for day and night - Unit dimensions - 6.3-inch H x 6.3-inch W x 3.3-inch D (external antenna), 7.1-inch H x 6.3-inch W x 3.1-inch D (internal antenna) Built-in inland maps provide 50-meter shoreline resolution throughout the United States, 10-meter shoreline resolution