Developed for cycling, hiking, skiing or mountaineering, these lightweight technical sunglasses are engineered to enhance performance outdoors. OS means one size or standard fit.Designed to perform throughout your adventure, Oakley Flak 2.0 Sunglasses feature Prizm lens technology which enhances colour and contrast to bring the detail into focus. The frame is constructed from lightweight materials and features secure Unobtanium earsocks and nosepads for a secure and comfortable performance fit.Lightweight O Matter frame material with ellipse metal icon accentsUnobtainium earsocks and nosepads for increased comfort and performance8.75 base lens geometry with HDOFeatures Prizm lenses to enhance colour, contrast and detail for an optimized experienceImpact protection - designed and tested under extreme high mass and high velocity circumstancesProtective soft vault includedColour: Matte BlackCareTo help maintain the High Definition Optics (HDO) of Oakley lenses, your new eyewear comes with a specially-woven electrostatic Microclear bag for cleaning and storage. Using it will preserve the superior optical quality of Oakley\'s pure Plutonite lenses. Hand wash and air-dry the Microclear bag regularly.