The visors provide added protection from the elements such as rain, waves, and glare. By reducing the amount of water on the screen you can spend less time cleaning it and more time fishing! It will also improve your touch screen usage and protect your card slots.
By reducing glare it makes the screen more visible so you can see the fish or contours you are following. Reduce the brightness to save battery life and reduce the temperature of your unit; improving its running performance and avoiding shutdowns.
Night-time boating is also improved by shielding your windscreen from the lights of the unit, making it much safer to commute at night.