Installation. Now switch your filter in 2-3 seconds with Freewell Quick Swap Magnetic system no more threading. Optical Glass. Made of using the High Definition Premium Optical glass double-side multicoated Zero chromatic aberration (color shift). Function. Circular Polarizer (CPL) Filter helps reduces glare from metallic surface increase color saturation and contrast. Coating. Each side of the glass element is coated with Waterproof, Dustproof, Scratchproof, Oilproof to make sure you are ready for all the adventures.