SWANS sunglasses are equipped with YAMAMOTO KOGAKU ’s specially developed PETROID lens.PETROID lenses are resistant to the extreme heat and cold as well as being resistant to heavy impacts. PETROID lenses are extremely light weight as well as possessing a superior optical performance. The material used for the PETROID lens is a plastic material called polycarbonate. Polycarbonate is used for various purposes such as the windows on airplanes, optical fiber and the body of mobile phones. In addition, an original superior anti-abrasive coating is applied onto the lens preventing scratches.