The I/O MAG XL is part of Smiths top end MAG series but in a large size frame. It uses their very latest technical features, including the MAG Quick Release lens changing system, so you can enjoy your day on the mountain. Coming with two lenses you are set for all conditions you are likely to encounter.Lens: ChromaPop Sun Green Mirror + ChromaPop Storm Rose FlashVLT: 9% (CAT 3) + 50% (CAT 1)Size: LargeLens Shape: SphericalMain LensChromaPop Sun Green Mirror With a 9% VLT this lens is suited for very bright cloudless days on the mountain, with a mirror coating to reduce glare from the sun/snow.Bonus LensChromaPop Storm Rose Flash With a 50% VLT this lens is tuned to optimise contrast and increase definition when the storms come in and conditions deteriorate.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.