The Mask OTG represents great value for money and has plenty of features to help you enjoy your time on the slopes. Frame ventilation allows warm moist air to escape and the dual-layer lens has an anti-fog treatment to keep vision clear. The frame is OTG compatible so optical glasses can be worn underneath and Bloc’s Click3 nose adjustment gives a more tailored fit.Lens: Brown Blue MirrorVLT: 19% (CAT 2)Size: Medium/Large Lens Shape: SphericalLensBrown Blue Mirror – With a 19% VLT and light brown base tint this lens is best suited for medium to bright conditions. The mirror coating helps to reduce glare.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.