This 55mm Ultra Violet (UV) Filter is manufactured from the finest solid optical glass, ground and polished to the most practical thinness. They are heat-treated to avoid any distortion or focal shift. The UV filter"s most practical use is the absorption of ultra-violet rays without increase of exposure, thereby preventing haziness and foggy effects in distant landscape. The UV filter is also useful as a general protective filter to leave on lenses at all times. Filters help to reduce dust and moisture from reaching your lens element and provide additional protection in case of drops or situations where scratching could occur.