Serengeti 7973 Norcia, Satin Black Frame, Drivers Gradient Lens A full 20% thinner and lighter, our ultra-light mineral glass lenses are made from only the finest materials, giving you the best visual Optics in the industry Double-injected stainless steel and elastomer temples for a lightweight, comfortable fit With superior Serengeti Polarization, the fatigue, discomfort, squinting and impaired vision associated with all forms of glare simply go away. Polarization available in select models only. Darkening in bright sunlight and lightening in overcast conditions. Serengeti photochromic technology allows your eyes to adapt to any light Serengeti spectral control technology filters specific light wavelengths, sharpening the way you see color contract and improving visual definition