DetailsGeared for speed. The Shift MAG™ gives cyclists and runners every performance advantage possible, from the superlight frame down to the nose piece. The coolest feature is no doubt the interchangeable lens technology. Snap the magnet on the side for quick, fingerprint-free lens changes. These Smith sunglasses come with unique Photochromic lenses, which shifts from clear to gray when exposed to sunlight so you can comfortably wear your sunglasses in a variety of lighting environments in most conditions. Flatter than most performance eyewear, the 5-base frames stay put with a two-position nose piece and no-slip temples. They give you a secure feel when you're going your fastest.