Garmin GNX 21 Information The Garmin GNX 21 is a marine instrument that provides a clear and concise display of important boating data, such as depth, speed, and wind. It features a 4-inch, glass-bonded LCD display with anti-glare lens coating for excellent readability in both bright sunlight and low light conditions. The GNX 21 also has a low power consumption, making it ideal for use on sailboats. Intro The Garmin GNX 21 is a versatile marine instrument that can be used for a variety of boating applications, including cruising, fishing, and racing. It features a bright, easy-to-read display that shows important boating data, such as depth, speed, and wind. The GNX 21 also has a number of features that make it a valuable tool for boaters, such as customizable user profiles, auto-scroll, and a low power consumption.