Use the 4 x 5.65" Clear Optical Flat Filter from Revar Cine to protect your lens from dust and inclement weather. Constructed from Euro-White Schott glass, this optically clear filter is polished for exact flatness, maintaining your image quality. It features a black edge seal that blocks unwanted light entering from the side of the filter, which is particularly useful when you're forced to tape the filter to your lens.