I bought this for a rarely used camera. It's still a valuable collector's item that I want to keep in excellent condition and that means I had to protect the lens. I only have filters with the Zeiss "T" coating made of German Schott glass on the cameras that I use a lot because I think they are the best multi-coated filters I can afford, but I can't spend the money on them spend on a camera I rarely use.
Any camera that is threaded to accept a filter deserves the protection that comes with a filter mounted in front of the actual camera lens. I would rather risk damaging the AR coating of a filter that can be easily replaced than risk damaging the actual lens on one of my cameras through cleaning and exposure to dust or chemicals in the air.
This brand of filter came carefully packaged and the filter holder that comes with the filter is well designed and provides excellent protection for the filter when it is not on the camera lens as I am using a different type of filter. This filter has multiple AR coatings on both sides of the filter and after comparing the results of identical images taken with the same camera using this filter and one of my prized and now unaffordable Zeiss "T" filters, I can say I see no difference can the results. I'm sure an optical lab could document some differences, but in the real world I can't tell any differences by comparing the test images,
This design works so well that I am slowly replacing the older non-Zeiss filters I have on my older lenses and cameras with these newer designs.