Photochromic lens technology helps to darken & lighten automatically in response to changing light. They help you adapt to changing light conditions so you’ll always perform at your best. The lens will allow 87% light through indoors, but only 47% light when outdoors. They also filter out 100% of all UV, even when the lens color lightens to help you see in dimmer environments where UV is still a threat. You get the added benefit of having lenses that aren’t too dark when the sun pulls a disappearing act, or too light when it knifes through clouds.