Fortis AV Switch Fishing Sunglasses, Our brand new Switch technology allows the lenses to darken substantially in response to UV light. The lenses contain light sensitive molecules that change shape and colour when ultraviolet rays strikes them. The lenses will begin to lighten as soon as they are away from UV light, gradually returning to their original state. Through a course of a session, whether that be at low light at dawn, stalking in the midday sun or sitting watching them fizz at dusk, your Fortis AV’s with Switch technology will be the perfect shades for all conditions. (Colours from pictures may vary).