This 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. Fits the lens perfectly. Great affordable alternative to the Camera.                                    Features            Replacement for Camera EF-S 17-85mm f/4-5.6 IS USM<br> Compatible with Select Lenses for High Quality Cameras<br> Prevent unwanted stray light from entering the lens<br> Extra protection from accidental impact<br> Designed to match the specific focal length of the lens<br>                                                                                                Package Includes            1 x EW73B Lens Hood for Canon<br>                                                            Extra Info            Compatibility: Canon lens EF-S 17-85MM F / 4-5.6 IS USM<br>