Here's what other sites are saying:
The Serengeti Fasano Polarized sunglasses with Advanced Polarized Surface Technology are an all around great sunglass. They are great for driving, hiking, or pretty much anything. The frames are made of nylon for light weight and durability. The lenses are Polar PhD which is photochromic - the lenses automatically darken in bright conditions.Key Features:Nylon frame is light and durableFrame has rubber nose pads and temple tips for comfortPolar PhD NXT lenses weigh less than polycarbonate and MUCH less than glassPhotochromic lenses automatically darken in bright lightPolarized lenses eliminate glareLenses block 100% UV (ABC).