1. Color-changing speed: The speed of color change is an important reference factor to consider when purchasing the Best 1.56 SF Mirror Photochromic Grey lens from China. The faster the discoloration speed of the lens, the better, for example, from a dark room to a strong light outdoors, the discoloration speed is fast, so as to prevent the damage of strong light or ultraviolet rays to the eyes in time. The Best 1.56 SF Mirror Photochromic Grey lens adopts the film-layer color-changing technology, and the photochromic factor adopts the compound with good performance, which has better photoresponsivity, so the color change speed is faster.2. Uniformity of color change: This refers to the uniformity of the color of the Best 1.56 SF Mirror Photochromic Grey lens from China in the process of changing from light to dark or from dark to light. The more uniform the discoloration, the better the color-changing lenses. The Best 1.56 SF Mirror Photochromic Grey lens uses high-speed spin coating technology and the color-changing film layer is evenly spin-coated, making the color more uniform after discoloration.3. Service life: The Best 1.56 SF Mirror Photochromic Grey lens from China will also undergo enhanced coating treatment after spin-coating the color-changing layer. In addition, the color-changing substances used in the Best 1.56 SF Mirror Photochromic Grey lens also have good photostability, so the color-changing function can be maintained for a long time and has a long service life.