What is the Smith Interlock series? It’s not a building-block toy for your niece, and it’s not a docking system for space shuttles. No, it’s the latest innovation in interchangeable sunglass lenses. With a simple twist of the frames’ rotating arms, you can release one set of lenses for another set. Buy a pair of Smith Interlock sunglasses with the included spare lenses, and you essentially get three pairs for the price of one--which, of course, leaves you extra bills for other gear.

You've heard about Smith’s cutting-edge visual clarity, impact resistance, and glare elimination. But why do you need multiple lenses, and which ones are best for which sports and lighting conditions? As conditions change from day to day (and throughout a given day), different lenses will optimize your visual performance, so it's best to select a pair of shades with lenses that serve your outdoor needs. Still out cycling when the sun goes down? Clear Mirror lenses will save the day by deflecting wind and eliminating glare from lights and water. Trail running in shady conditions? Ignitor lenses will improve visual definition and depth perception by highlighting shadows. For bright days on the water, look to Polarized Brown lenses to cut out eyeball-searing glare. Yellow lenses come in handy when the light gets super flat on cloudy days, and mirrored lenses reflect very bright light away from the eye.

Combine this incredibly practical versatility with Smith’s exceptional lifetime warranty, and the result is utter radness. It’s as if Smith researches this stuff in real outdoor situations…Oh wait. They do.