Serengeti Siena Sunglasses Base Curve: 6Rx; Temple Length: 135mm; Lens Size: 54.6 x 37. 6x 51.8 mm S-Flex Unparalled comfort. Revoluntionary design. Made of durable, lightweight monel and beta titanium, the S-Shaped temple design adjusts ot the contours of your head for ultimate comfort. With its versatile brown lens, the Drivers Polarized lens peforms under cloudy and harsh light conditions. Plus, you get the added protection of the Serengeti polarizing technology. 18% transmittance lightened lens/10% transmittance darkened lens.