Are sunglasses with a reflective optical coating (called a mirror coating or flash coating) on the outside of the lenses to make them appear like small mirrors. The mirror coating decreases the amount of light passing through the tinted lens by a further 10–60%, making it especially useful for conditions of sand, water, snow, and higher altitudes. Mirrored sunglasses are one-way mirrors
When light reflects from water, asphalt, or other non-metallic surfaces, it becomes polarized. That is, the reflected light is usually vibrating more in one direction than in others. Polarizing sunglasses reduce this reflection, known as glare, but only when the polarizing lenses are oriented properly.