Oakley engineering takes performance to the next level and brings style along for the ride. Flak 2.0 offers a standard size frame with enhanced lens coverage, and every millimeter of the lens is optimized with High Definition Optics® in a ruggedly durable yet lightweight design. Designed to push your limits with patented XYZ Optics® for razor-sharp clarity and secure grip of Unobtanium®. The sunglasses come with: The XL edition offers enhanced lens coverage and specialized lens curvature for protection against sun, wind and impact. Unobtanium® earsocks and nosepads keep glasses in place, increasing grip despite perspiration. Patented High Definition Optics® (HDO®) provides superior optical clarity and razor-sharp vision at every angle. O-Matter™ stress-resistant frame material is both lightweight and durable for all-day comfort and protection. Prizm Prizm™ is a revolution in lens optics built on decades of colour science research. Prizm™ lenses provide unprecedented control of light transmission resulting in colours precisely tuned to maximise contrast and enhance visibility.