The BH-672 Lens Hood from Tokina is a replacement lens hood designed specifically for the AT-X 70-200mm f/4 FX VCM-S lens. This dedicated petal-style lens hood is designed to match the specific focal length of this lens.
Lens hoods are primarily made to prevent unwanted stray light from entering the lens by extending and shading the end of the lens. In addition, you get the benefit of extra protection against the elements and accidental impact.