... It seems to filter manufacturers still to be impossible to get a few thick zones on the rings their filters. So also the B + W. Every time I aufschraube this as a second filter on the B + W UV blocking filter, then I need a tool to separate the two again. It does not matter if they were not at all or only slightly tightened. Suffice the tightening torque of the rotary tables of the polarizing filter. And the fixed ring is very narrow.