Oakley engineering takes the cake as far as style and performance. The Flak 2.0 offers a standard frame size with enhanced lens coverage. The lens on the Oakley Flak 2.0 features Oakley’s patented High Definition Optics (HDO) which provide you with razor-sharp vision from any angle and superior optical clarity. The XL edition gives you enhanced lens coverage and curvature for maximum protection against sun, wind, and impact.