The Oakley SI Ballistic M Frame Alpha is designed to be compatible with a wide range of helmets and helmet-mounted night-vision devices. The High Definition Optics lenses offer 100% protection from harmful UV rays, and are made in a hybrid shape to create a wider field of view. The lightweight O Matter frame is impact and chemical-resistant for ultimate durability, and features an Unobtainium nose pad to stay in place, even when wet. A trapdoor exchange on the frame allows you to rapidly and easily change lenses to maximize visual performance in any environment. Alpha M Frame lenses are fully compatible with the Halo goggle and Halo-Alpha Gasket accessories for total versatility. Constructed to meet stringent ANSI high-mass and high-velocity impact standards, these glasses deliver ultimate optical performance without distortion.