These glasses are equipped with polarized lenses. The sun's rays reflect off of surfaces such as sand, water and snow at different reflection rates causing glare. Crossfire Polarized lens technology prevents glare by filtering out the reflected light and glare from above resulting in enhanced vision in harsh environments. Don't be fooled bt some manufacturers! Only 2.2 mm polycarbonate polarized lenses will pass ANSI high impact testing. Acetate will shatter if high impact occurs, putting the user at great risk!