On the plus side, K&F is pricing this reasonably.
They also throw in their obligatory three micro fiber cloths, which I appreciate.

I ordered this in 82mm for my 135mm f/1.8 lens and it was tough going. I just could not get the center focused, and that particular lens is insanely sharp.

So plan B. I reduced the threads and attached it to my Voigtlander 65mm Macro lens with a 67mm filter diameter. Those are the images presented for your perusal.

When pointing in the direction of the sun, you can clearly see where the refraction begins (bamboo fountain images). One was taken with the filter horizontal, and the other was vertical. The filter can be adjusted just like a CPL filter can. If you like that look, great. I was hoping for a more soft transition.

It only occurs against the light however.

Moving on the the Agapanthus flowers (purple). Again I am taking these with the 65mm macro.
The closeup gets the job done nicely. The center is very sharp (the lens is very sharp itself), so the filter is not interfering here. If I pull back a bit (image with many flowers), there is no sharpness anywhere to speak of. The parts that are supposed to be out of focus gets a bit wonky in my opinion.
That may be what you want, up to you.

So, I have found that up close, it does a great job of giving you a nice effect.
But pull back, and it's soft pretty much everywhere.

I suppose if they had removed more glass from the center edges, it would handle better further back.
So, for close up work, you get the center sharpness and a soft diffusion (watch the sun though)
It may have some portraiture abilities, depending on what you desire.

It's a neat filter, but I could not get great results unless I was really close to a subject. Then it was sharp as a tack, meaning it did not get in the way of the lens.

Update: I let the sun go down a bit and decided to try my 20mm f/1.8 with this filter. It's cropped down quite a bit, but as you can see, the subject flower is very crisp. Look at that background! Especially the top horizon.
So in my bit of experience, this filter does very well wide open and starts to flag as you extend the focal length. Makes a bit of sense now. I had a case of UE...User Error.

I personally love that image which I casually knocked off. With some foresight and prep, this filter can produce some trippy images.

Pretty sweet filter.