Until you take it to ND 350 O 400 it doesn't make the effect of X so it's very wearable at a very affordable price, it has a slightly warm color temperature throughout the image.

For this price you can't do much better! There is some X artefacting at the darkest setting, but otherwise this is a fantastic value for a variable ND. Using this on my Sigma 16mm on an a6400

I love this product! Works perfectly! I don't need to try high priced VND filters so I'm not sure how it compares to Peter McKinnon VND or similar. For $20, I get my bang for the buck. I have already ordered a 2nd as I am running 2 cameras arriving today. I'll probably do an unboxing video for this next one.

UPDATE: I was approached by a company rep and offered a replacement filter. I received it today and did a quick test. This filter seems to be much better. There are no corner shadows or black spots when shooting towards a light source. Haven't tried it in the field yet, but looks like it will be ok. Either way, impressive customer service.

ORIGINAL: After reading all the reviews, I decided to buy this filter because my budget was tight. I used it with a 24-105 f/4 L lens to take some sunrise and sunset photos. It's absolutely awful. On the right side of the filter is a black shadow that gets stronger with each step. I wish I could return the filter but I already threw away the packaging :( Have to throw away this filter as it is totally unusable...

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....

I shoot a lot of video with my Canon, and to get that cinematic 180º effect with the shutter speed, I often have to reduce the amount of light coming in when shooting at 30fps. This is where the ND filter comes into play.
In this case I am still starting but it is difficult to know which way I have to turn, I would like the filter itself to have a stop to indicate me the maximum or minimum.
Otherwise, this filter does not produce any distortion like some filters I have seen in some tutorials, nor dark halos. A great buy, if you are going to use it with different lenses, I recommend to buy some rings to adapt it.

Well packaged and delivered the third day. The K&F Concept filter itself feels to be of good built quality with a metal frame holding the glasses in place. The action to adjust the stops is smooth. I bought this mostly to save some bag space so I'm not having to either stack and carry multiple ND filters.

Considering the price, the image quality is reasonable. I did not experience the dreaded X from the graduated filter. You can see some product and test images I did at home to test the product. ( the camera settings remained the same throughout the test images with adjustment on just the ND settings).

EXCELLENT value for money.
To the touch it shows good material, there is nothing plastic, it seems resistant and the turn is soft enough to move it without a problem but it will not move due to a silly blow.
The image quality is very good, it adapts perfectly to the lens and I have not noticed vignetting.
It is true that if it exceeds the maximum, the "x" effect is appreciated, but knowing it, there is no problem.

In short, I would buy The K&F Concept ND Filters again. For that price you can't ask for more.

Cheap, practical, useful, and perfect. Those are the words to describe it simply. Very good quality. It's advisable. It comes with a box to store the filter and keep it covered and/or safe from any sudden movement or harmful damage. The size of the thread is perfect and as the product says it is 9 layers. Enough to help you in some sessions ☺️. I recommend it to you. I hope it arrives in perfect condition.