I have had problems with some of the Cokins, but not all, the only way I will purchase one is if I can try it on a simular length lens that I will be shooting with, it seems as if for some time, they had some bad quality control problems, which lead to a large amount of them being distored, now the current cokins that I have been purchasing have been fine with no problems at all, but it does seem like they went through a bad period several years ago.