1, high quality color changing glasses lens surface, no trace of scratches, abrasions, hairy surface, pockmark, the lens will be oblique to the light observation, the brightness is very high. The lens internal no spots, stones, streaks, bubbles, cracks, light transmission bright. 2, color changing glasses two lenses must be the same color and no difference lenses, color change to uniform, can not show several colors, no “yin and yang color”; a see sunlight, color change time fast, no sunlight, color receding time is also fast. Poor quality lenses change color slowly and fade quickly, or change color quickly and fade slowly. The worst color-changing glasses do not change color at all. 3, color-changing glasses two lenses should be the same thickness, not a thick and a thin, otherwise, it will affect vision, damage eye health. The thickness of a single piece should also be uniform, if it is a color-changing flat lens, the thickness of about 2mm is appropriate, the edge is smooth. 4, wear without any feeling, not dizziness and swelling, observation objects are not blurred, not deformed. When you buy, hold the glasses in your hand, single eye through the lens, look at distant objects, shake the lens up and down, distant objects should not move illusion. 5, fast color change: high-quality color-changing mirror, the environment has a faster responsiveness, the color-changing mirror will be placed in daylight exposure within about 10 minutes, that should reach the maximum color depth, otherwise it means that the color-changing quality is poor. Will have been in the daylight discoloration of glasses moved to a dark place, the lens re-luminate time of no more than 20 minutes for the quality of color-changing glasses. 6, protective, high-quality color-changing glasses, can block 100% of ultraviolet A ultraviolet B, for the wearer to provide the most effective UV protection.