The Huub Aphotic Photochromatic Goggles have special patented photochromic dyes that cause the lens to activate & darken when exposed to ultraviolet rays from the sun. When the UV light fades, the lenses fade back & as the light conditions change, the level of tint adjusts. They are designed to fit the face perfectly with a lightweight feel. Features From clear to dark for ultimate performance Designed to fit the face perfectly Anti fog & scratch resistant lens Self-regulating lens that delivers comfort & vision needed to maximise your swim