The Nikon HN-36 lens hood is designed to be used in combination with the AF-3 Gel Filter Holder. This lens hood is necessary since the lens' original hood can no longer be used once the Gel Filter Holder is attached to the front of the lens.
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.
