Serengeti Sunglasses Rivoli 7916 Shiny Matte Black Mineral Polarized 555nm Green Photochromic are from the Serengeti Flex series and they will adjust to the shape of your head for a supremely comfortable snug fit. The lenses are of course Serengeti’s unparalleled photochromic lenses which will lighten/darken for optical light transmission in any condition and also reduce eye strain and fatigue.