The Ray-Ban RB3548N Hexagonal Evolve Photochromatic Flat Lenses Sunglasses is the combination of a circle and a square shape frame that is perfect for both women and men. The new hexagonal round metal shape features thin coined profiles with super thin temples and flat Evolve photochromatic lenses. The 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.