The M is a downsized version of the Flight Deck, built for a smaller face. This mid-sized frameless design draws inspiration from helmet visors of fighter pilots Рresulting in a massive field of vision for the wearer. This wide view is complimented by a whole host of Oakley\'s top end tech features.Lens: Prizm Torch Iridium VLT: 17% (CAT 3)Size: MediumLens Shape: ToricLensPrizm Torch Iridium is suited for variable to sunny conditions; the Iridium coating reduces glare from sunlight reflecting off the snow, whilst the rose tint increases definition in flatter light. Prizm technology blocks specific wavelengths of light whilst boosting others to provide maximum contrast and enhanced visibility. This greater clarity results in reduced reaction times and increased performance over a wide range of light conditions.Visual Light Transmission, VLT, refers to the amount of light that penetrates a lens. A low percentage means less light passes through and a higher percentage lets an increased amount of light through. A lens with a lower VLT rating is better for bright conditions; where as one with a higher VLT is more suited for overcast and snowy days.