I bought this filter tempted by the derisory price and the fact that it is small lightweight and that it allows me in one accessory to have several plates together, as I already have plate filters and moreover 150x150, which are really inconvenient to carry around .

The product looks really good packed inside its case, it is very light and of metallic material with the various notches indicating the ND set. Maybe on this one I would have liked it to actually say how many stops you were at without me having to do the math every time to figure out how many NDs I was at.(but maybe space doesn't allow for that).

I am happy with the purchase I made because it exceeded my expectations,
I tried it with focal length above 50mm where I didn't find any problem and the image turns out with uniform exposure without any halo, it must be said though that I also tried it only at ND400 without trying the intermediate stops so I couldn't tell what happens at lower stops; Unfortunately being in full daylight didn't allow me to do other tests..(of course if I can I will update by adding some more details).

Finally I think that in terms of quality/price there is no better around, at least for the ones I have tried and K&F improves year after year...

I enclose a few photos to make yourself aware of the product and the result....