The voigtlander lh 40n lens hood is designed for use with the voigtlander 28mm f28 color skopar sl ii lens with an aps c sensor or the 40mm f20 ultron sl ii lens with a full frame sensor it prevents unwanted stray light from entering the lens and causing flare and by extending the end of the lens adds extra protection from accidental impact it also features a front thread of 52mm