At high altitudes, intense light, dazlle and variations in lighting conditions are extreme. Fresh snow reflects 85% of solar radiation and the uv index increases 10% every 1,000 m. Mountaineers need to be able to rely on materials that are absolutely safe and which they do not need to think about. The ever popular Colorado is ideal for larger heads. Removable side shields and moldable temples. Includes the Spectron 4 polycarbonate lens, light but with excellent shock resistance, this verstile lens is suitable for all types of sports activities. Flash + Anti glare treatment. Lens are category 4,( 95% visible light reduction).