In case you run or ride your way into a parallel universe, we suggest you carry an extra set (or multiple sets) of lenses to adapt to the potential for shifting light conditions. And while reaching another universe may not be realistic (yet), changing weather and lighting is a good reason to always have a variety of the Smith Parallel Replacement Lenses handy. In the rare event your Delorean hits 88 miles per hour and you travel through time, the impact-resistant Carbonic lenses feature Tapered Lens Technology (TLT) to limit distortion. Product FeaturesMaterial: Carbonic TLTPolarized: Compatibility: Smith ParallelRecommended Use: replacement lenses for changing conditionsManufacturer Warranty: lifetime