This 40.5mm HD Multicoated 99% UV Filter from H& Y Filters blocks UV light and reduces the bluish cast of daylight that can affect color accuracy, especially at higher altitudes. Multicoating reduces unwanted internal reflections and ghosting for optimal sharpness and 99% light transmission. In addition, the filter coating repels dust, fingerprints, and water, making it suitable for use in harsh environments and easy to clean.