The Voigtlander LH-20 Lens Hood is specifically designed for the Color-Skopar 20mm f/3.5 SLII lens. By extending and shading the end of the lens, it prevents unwanted stray light from entering the front element and causing flare. Additionally, since it protrudes beyond the end of the lens, you also get the added benefit of some extra protection from accidental impact. The hood includes a cap that protects against dust, dirt, and scratches when the lens is not in use.