Zeikos 82mm Multi-Coated Circular Polarizer CPL Glass Filter w/ Rotating Mount For Sigma 10-20mm f/3.5 EX DC HSM, Sigma 12-24mm f/4.5-5.6 & Sigma 24-70mm f/2.8 Lens Reflective Technology: Glass blocks and prevents certain light rays that cause reflections and glare, giving your photos a more vibrant look! The effect can be seen through the viewfinder and can be changed by rotating the filter frame. The effect can be seen through the viewfinder and changed by rotating the filter Filter factor varies between 2.3 and 2.8, according to how the filter is rotated and its orientation to the sun Best results with SLR cameras Designed for lenses specifying a 82mm filter thread size