Keanon is one of the few sunglass brands that actually manufacturers their own lenses. Their SR-91 polarized lense answers the shortcomings of existing polarized lenses. Glass is heavy and shatters, CR-93 is brittle and not impact-resistant, while polycarbonate offer a dull view and scratches easily. SR-91 was tested in independent labs and confirmed to be the only polarized lens that offers razor-sarp clarity, impact-resistance and glare-reduction all in one ultra-light and durable lens. All of the good, non of the bad!