Engineered with sport performance in the forefront of their mind, Oakley's Flak Jacket XLJ sunglasses were made to go further, train harder, and excel no matter what the conditions. The XLJ designation lets you know these large lenses are curved at the bottom to fit around your cheekbones, and they are completely interchangeable. This means you can go from a golf course, to a race track, even up a mountain, using lenses optimized for that specific location. Do more, go further, and don't forget your Flak Jacket XLJ.