Lens hoods are primarily designed to prevent unwanted stray light from entering the lens by extending and shading the end of the lens. In addition, since the end of the lens is extended you also get the added benefit of some extra protection from accidental impact.
This plastic snap-on lens hood is designed for wide angle lenses with a focal lenght as wide as 24mm. Includes plastic hood cap.
Note: Not for lenses where the filter threads rotate, such as some zoom lenses.