FIBER OPTIC STRANDS (0.015625 dia.) wrap around the back sides of the "half circles" shown above on the black revolving prong sights. The strands capture ambient light rays which travel to the 2 end points of the individual strands. The highly visible end points of the strands can be seen in the picture above as RED or GREEN Dot Sights that GLOW for sharper aiming and shooting accuracy!