The Tokina BH-551 Lens Hood is designed for the Tokina 100mm f/2.8 Macro lens. This dedicated lens hood is designed to match the specific focal length of this 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.
