The Oakley Polarized XLJ Flak Jacket might resemble the popular Half Jacket XLJ designs but there's more to the innovations than a redesigned frame. The Polarized XLJ Flak Jacket represents a new generation of Oakley sport eyewear performance. The interchangeable polarized lenses have a permanent hydrophobic lens that repels skin oil rain and sweat to optimize optical performance. The lenses also resist smudges and clean easier than previous eyewear making the design better suited to endurance sports and extended climbing and backpacking. Polarized lenses are ideal for reducing the glare from reflected light on water and snow. While most sunglasses manufacturers rely on sandwiching a layer of polarized film between two lenses and calling it good Oakley designs their Polarized XLJ Flak Jacket lenses through a special liquid fusion technology that introduces the polarized filter while the lens material is still in a hot liquid state bonding the film at a molecular level that doesn't leave you peering through the glue residue that other polarized lens manufacturers leave behind. While some people found the Polarized Flak Jacket lenses easier to change than the Half Jackets it's all really a matter of getting used to changing lenses. Like learning anything new changing the lenses the first time around takes an extra moment or two. The XLJ lens design offers more vertical sweep or coverage than the standard Flak Jacket designs an essential feature for athletes with larger faces or those who tend to watch their foot placement more than others. After that you can swap out lenses in a few moments and quickly adapt to new light conditions. Like the Oakley Half Jackets the Flak Jacket has a featherweight O Matter® frame with Unobtainium earsocks and the proven three-point fit. Unobtainium tends to grip more when wet so you don't have to worry about your Flak Jackets giving you the slip before you reach the finish line.