The Canon ET-60 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.
★★★★★ Perfect fit on my Canon lens and does exactly what it should—blocks stray light for clearer, contrastier shots. The extended hood also gives me peace of mind against accidental bumps. Great value and highly recommended.