Canon EW-73B Lens Hood for EF-S 17-85mm USM & EF-S 18-135mm IS Lens

The Canon EW-73B Lens Hood is 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.

Additionally, the "petal" shape of this lens hood maximizes the amount of hood coverage for the minimum amount of weight and hood area. Dedicated lens hoods, such as the Canon EW-73B, are designed to match the specific focal length of the lens it was designed for.