Changing outdoor light conditions doesn't require changing eyewear anymore. SmartLens does all the changing automatically. The lens is "UV reactive", so it responds to the amount of Ultraviolet (UV) light it receives. It lightens or darkens as needed...going from clear to gray in just seconds. Why spend the money to buy multiple pairs of eyewear? Micro-fiber bag and lanyard included. Complies with ANSI Z87.1-2010.