Super tough, High Performance PhotoChromatic™ shell manages pin brightness. If pins get too bright they can create starbursts that make it difficult to see the vitals. Black Gold’s revolutionary and patented PhotoChromatic shell, which covers the sight’s fiber optic strands, turns purple when subjected to natural UV light. This automatically tempers the light which eliminates any pin flare. The result is perfect pin brightness from dawn to dark! Recently redesigned, the shell is 80% tougher, changes color even faster and gets even darker in bright light!