Voigtlander LH-9 Lens Hood for 35mm f/1.7 Ultron Lens (Silver)

The silver from is 2.5" wide in diameter and vented, so as to not completely block the viewfinder. Lens hoods are primarily designed to prevent unwanted stray light from entering the lens by extending and shading the end of the lens. Because the end of the lens is extended, you also get the added benefit of some extra protection from accidental impact.