Sports Frame is Lightweight But, for Safety Eyeglasses with Wraparound Design that Provides Increased Side Protection and Peripheral Vision Photochromic adaptive transition lenses readers will gradually change color within ten minutes under strong sunlight. Does not change color on cloudy days. UV400 rated sunglasses are essential for filtering out sunlight reflected glare and protecting your eyes against long term UV damage when you go out Fashion sports frame, Outdoor UV protection drivingreading glasses If you have any question, please feel free to contact us. Photochromic glasses have lenses that change tint depending on the weather or surroundings. The benefit of photochromic lenses is that in dull, overcast weather or darker surroundings (like running or cycling through woods or early / late in the day) they will lighten. But in bright, sunny conditions they will go dark. Photochromic lenses are most popular with cyclists, runners, skiers, tennis and outdoor reading enthusiasts.