The Interlock 01's Patented Interlock Interchangeable sunglass lens system creates a design allowing easily interchangeable lenses perfect for the running trail, golf course, or casual wear. Distortion-free, 8 base TLT Carbonic lenses to provide precise optical clarity and maximize coverage while minimizing peripheral exposure to sun, wind, and glare. A medium fit and Grilamid TR90 frame insure lasting comfort & durability. 14 replacement lens tints to choose from and as always the Interlock 01 is backed by Smith's lifetime warranty.