Your favorite mountain bike trails have you flitting in and out of trees and over mixed terrain, and Oakley’s Prizm Trail Flak Jacket XLJs are purpose-built to excel in these variable light conditions. The Prizm Trail lenses are optimized to help you easily distinguish obstacles such as rocks, sand, and hard-packed dirt so you always know what’s coming up. The Prizm lenses are just the beginning though. The frames use Oakley's lightweight O-Matter material and feature a semi-rimless design for an extensive field of view. Their Plutonite lenses feature High Definition Optics for the highest level of optical clarity and they filter 100% of all UV rays while meeting the highest impact protection standards. The XLJ designation means they provide more coverage for medium to large faces. Plus, the ear and nose pieces are made of Oakley's Unobtainium to keep your glasses exactly where you want them and two nose pieces are included with every frame for a perfect fit.