The FACTOR D-MAX'S Polarized interchangeable lens system creates a sleek and subtle design allowing unobstructed peripheral view perfect for the running trail golf course or weekend ride. Smith's Interchangeable lens system utilizes distortion-free 9 base Carbonic TLT lenses to provide precise optical clarity and maximize coverage while minimizing peripheral exposure to sun wind and glare. The thin and flexible TR90 frame provides a universal fit while the Lifetime Warranty ensures against any manufacturers defects.