Mirror coating is like the name indicates, is a mirror coating applied to the front surface of the lens. A special treatment is applied to the front surface of each lens through a vacuum process that allows the lens to take on the properties of a two-way mirror. Mirror coatings can reflect the light rays that are emitted from surfaces such as water, snow and ice therefore making the lens darker than an average un-mirrored lens. Many Mirror coated lenses may also feature AR coating on the back of the lens for improved vision and reduced back glare.