The FACTOR'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.