Every price sign is going to have to deal with extreme heat at one point or another: heat from the sun, heat from internal electrical components, and more generally, rapid and repeated changes in temperature. Over the life of the sign, these environmental variations can be tough on a sign, and can reduce the life of the sign if it does not deal with heat properly.
Some manufacturers cover their LEDs with Plexiglas, mainly to protect them from weather and other external elements. While this method does do a good job of protecting the LEDs from harsh weather, covering the LEDs entirely traps heat from the internal components as well as the Sun, essentially baking the LEDs right in the sign itself.
Other manufacturers simply leave their LEDs fully exposed to direct sunlight, and while this helps with trapped heat, LEDs directly exposed to sunlight will fail more rapidly than those that are not. Furthermore, LEDs that are exposed to direct sunlight often appear dim and are much less legible than LEDs that are shaded.
Skyline features unique, patented aluminum hoods over each protruded LED to improve contrast and legibility, protect the LEDs from hail and UV light, provide better viewing angles, and deliver better cooling. Since each LED is covered by an aluminum alloy hood, the LED is shielded from the sunlight, improving its longevity.