Oakley flak jacket replacement lensesfrom day one the oakley goal with flak jacket was to create world class sports equipment training and competition can take you from bright sun to overcast skies and everything in between so they engineered an interchangeable lens design that lets you adapt with extra lens sets youll always have the best optics for current conditions and youll be ready for whatever the sun does ten minutes from now the xlj lens shape offers more coverage and multiple