The 4 x 5.65" Linear Polarizer from Revar Cine is made of SCHOTT B270 optical glass with an inner layer of premium polarization foil. It is designed to fit in standard 4 x 5.65" matte boxes or filter trays. This nonrotating filter can be used with the Revar Cine 4 x 5.65" 138mm Rota-Tray or 138mm Circular Polarizer Pola+ to make a 2 to 8-stop variable ND. This can be purchased together as a kit in the Variable ND Kit.