I did some research on the internet and found a lot of recommendations for Marumi filters. I also found an independent photo testing group that tested 100 brands and rated them on quality. They rated Marumi filters as being the best on the market. I had never heard of them until I looked into buying a new set of filters. What I understand Marumi made filters for the Japanese market with little going overseas. The internet seems to have changed that. While they are still relatively unknown they are now sold world wide. They are also less expensive than most of the more popular brands. I have used the Marumi CPL Digital for the past six months and find it of very good quality, it turns smoothly to set it, other filters thread on and off easily and with no hang ups and has worked as well as any I have ever used.