The Marumi Slim Fit Circ. Pola Filter 37 mm is an extra-thin filter that is ideal for use with wide-angle lenses. The filter is 7 mm thick, while a standard CPL filter is 10.2 mm thick. The polarizing filter achieves greater color contrasts in outdoor photography. Blue skies become brilliantly blue skies. With a polarizing filter, you can photograph reflective objects like water or windows more effectively: they become transparent and no longer reflect incoming sunlight.