This screw on lens hood is specifically designed for use with Nikon's NIKKOR Z 40mm f/2 Lens. It is primarily used to prevent unwanted stray light from entering the lens by extending and shading the end of it. Crafted to perfectly suit the specific focal length of the lens it is designed for. Additionally, this hood features a non-glare matte finish on the interior surface to further prevent or limit lens flare. Also, since the end of the lens is extended, you get the added benefit of some extra protection from accidental impact. The barrel shape of this lens hood maximizes the amount of coverage for the minimum amount of weight and hood area.