This Blue Adapter filters through a strong blue light, great for penetrating fog and smoke, and great for signaling. Improve night-time visibility and avoid easy detection with these colored filter adapters. Durable with an anti-roll design, they improve map reading, navigation, and tracking. Features Uses a toughened ultra-clear glass lens with anti-reflective coating that provides both heat resistance and maximum light penetrability Made from PC 2805 plastic, created by Bayer Material Science AG. PC 2805 plastic can withstand impact and has anti-aging components. Easy to attach, easy to remove Inside diameter: 1 5/8"