If your pins get too bright they can create starbursts. This starburst effect makes it difficult to see your target. Montana Black Gold’s patented PhotoChromatic shell covers the fiber optic strands and turns purple when under natural UV light. This automatically adjusts pin brightness in any light conditions resulting in perfect pin brightness all day long. The shell has been recently redesigned and is 80% tougher, adjusts faster, and is even darker in bright conditions without diminishing pin brightness in low light conditions.