Well, it depends, what focal length do you need? What field of view do you like? From there, looks into all the possible lenses in these settings. Do you need a photo lens or a cine geared lens?
I just hope this will sit between nicely between Fotodix 99$ and Metabones 399$ smart adapter.
Which camera are you using the filters with? I'm curious to know your result with the 6-stop and 10-stop
These aren't designed for cinema camera, these are photography filters. I think only the Red dragon sensor does ok with straight non-IR ND filters. Cool video but not to be confuse with cinema ND and NDIR filters.
These filters are build with photography in mind. They all come in 3 version (3-stop, 6-stop and 10-stop) They aren't build for cinema camera since they don't cut IR which photo camera sensor does.