These glasses have category 3 SINTEC Polarized lenses. The category 3 EU classification means they are recommended for use in bright light in mountainsdeserts and at sea. SINTEC Polarization reduces glare, especially from flat surfaces which is more comfortable and makes it easier to see. They also filter out some blue light which increases contrast and improves depth perception in a range of weather conditions. All this helps to reduce eye strain. The mirror coating also helps to reduce the amount of light getting to your eyes. The frames are nickel free and the screw hinges are stainless steel so they are hypoallergenic Lens base 642g