Ray Ban Hexagonal SunglassesThe Evolve photochromatic lens treatment allows a gradual change of lens color from a lighter shade to a darker shade within three minutes when exposed to UV light outdoors. No other light will result in the color change. Within five minutes of stepping back inside, the Evolve lenses in the RB3548N will gradually change back to the original color! Made from high quality glass, Ray Ban lenses are prescription ready.