Just noticed this on 2filter, my go-to website for filters: *Important Info on Circular Polarizers: For years 2filter has suggested to purchase step up rings to avoid buying double the number of expensive filters. This made sense especially with the original much thicker old style circular polarizers. Now that all the filter makers have made the mounting rings as tiny as possible and they are getting even thinner. The mounting rings are so slim, if you get a step up ring stuck on your CP filter you may not get the two apart. 2filter’s new advice in 2012 especially on thin circular polarizers is to purchase a separate one for each different mm size lens mount you want to use a cpl on. We ourselves now have a B+W 72 to 77 step up stuck on a slim 77 circular and just can’t them apart. Not the first time it has happened to us, maybe a tiny speck of sand got in the filter threads and now is acting like a break. Freezing the stuck filters sometimes help but not this time, neither did the filter wrenches. This isn't the first time I've heard of a polarizer getting stuck on a step up/down ring, but I've never read a universal recommendation against using them. The idea of buying a polarizer or circular ND (and juggling with them in the field) makes me shudder. What is everyone's thoughts on this?