I bought this variable ND filter for the 18-55 lens with 52mm diameter on my Nikon and it turned out to be perfectly compatible with the declared lens diameter and screws on without problems.
This is a variable filter, which allows you to reduce the light gradually, from 2 stops up to 11 stops.
I found the ability to gradually adjust the density of the filter very useful. This allowed me to obtain optimal results in different situations, without having to change filters every time.

In the attached photos you can see the difference between the photo without filter and the one with filter applied and the longer exposure time.
The attached tests were done with exposure times between 2 and 8 seconds.
Obviously to achieve excellent results it takes a lot of practice and you need to know how to use manual focus because once the filter is inserted, if the light is significantly reduced the lens has difficulty focusing automatically.
For the moment I am very satisfied and I would recommend it.

This filter is very made of aluminum, slim and very light. Very well constructed.
Because this filter is 52mm , but designed to fit a 50mm size lens, you will not be able to :
1. attach your lens cap (maybe a 52mm lens cap would fit)
2. attach your lens hood
3. attach any other filters to this one. You are able to attach 50mm filters to your lens, and then stack THIS one onto those filters. I did this with my CPL filter, but found it difficult because I had to rotate the CPL , and then rotate the Variable ND filter, so I removed the CPL for now.
Also, I need to investigate whether it is even advisable to use a CPL and ND together because of the low-light.

It is really a nice feature of this filter to incorporate 1 to 11 stops on this one variable filter. It makes it easy to dial to the stop that you want to use, but I found it a little confusing. The stops are labeled with Min on one end, Max on the other , and 8 dots in between.
So I'm not really sure what dot corresponds to what ND stop, there are supposed to be 11 stops, but there are only 10 markings.
Also , there is no lock at the beginning or end of the 10 stop markings.

Anyway , I've been experimenting and getting to learn how to use it.
I see how it it very convenient to have only ONE Variable filter, instead of several. Much less exptensive, much less complicated. But it is going to take me a little bit of time to learn how to use it efficiently.

I’ve mainly been using this ND filter on my Rokinon 16mm T/2.2 cine lens and it works like a charm. No weird color shifting or distortion to my images. Easily screws on/off, smooth rotating ring. No hard stops, but that’s to be expected from a budget friendly filter. Overall I’ve grown to love K&F products and this ND works great & has more than enough stops to help me achieve the proper exposure

The 49mm ND filter came in a typical filter case along with three pieces of microfiber cloth.

The filter looks well made. Clear markings on the filter and so easy to rotate and set it to the desired setting. It is easy to mount the filter onto the lens and remove it. The lens cap fits over the filter just fine.

I shot quite a few images, the light gathered by the lens is reduced as the filter ring is rotated to a higher stop. Happy with the results for occasional use. I can use this filter for long exposure to get say motion blur. My initial review with some shots of the trees showing the light reduction got rejected and so not including them this time.

There wasn't a 43mm available so I ordered the closest option, which was the 49mm and used a step-up ring to fit it to my EF-M 22mm. There is a slight greenish tint to the glass, though it does not colour the footage significantly enough to trouble me. Unlike some other variable ND filters I've used, this one does not produce a dramatic X at the end of the range, though some slight X-ing is present when going beyond the maximum.

I am leaving this filter on my 22mm permanently. FYI if you want to add a lens cap to this you will need a 52mm cap.

I’ve never used a variable ND filter, so this was really cool to be able to test out. It came in a protective plastic hard case along with three microfiber cleaning cloths. While slightly heavier than normal nano filters, I still was surprised at how lightweight it was comparatively.
Adjusting the strength of the ND was smooth as butter. The ring glides with minimal effort to achieve a lighter or darker filter between the min and max settings. If you keep twisting it past these points, it goes through the same grading scale until it reaches the starting point again. The threading is well made, so installing it on my lens was easy.
After some testing, I haven’t seen any vignetting or loss in sharpness. There is only minimal color shifting, and I didn’t notice any until around the ND1000 mark.
The image quality is fantastic with this, but the really beauty of it is the convenience. While it doesn’t take a long time to change a filter, it becomes annoying quick having to switch multiple times. It also takes up precious space in your kit when you are trying to travel light. With this, there is no more fumbling with multiple filters trying to get the right combo for the shot. If I need to adjust, I just give the ring a quick twist and I’m good to go. And instead of a case with multiple filters taking up space, I have one filter that does the job of a whole set. It’s absolutely fantastic. Nice job K&F!

My first foray into filters and I'm excited to use this beyond testing indoors and out in direct daylight. The filter comes in a plastic case, which I appreciate. The lens fits great on my Nikon and I love how it's a variable filter, so you're able to shift the lens to create a more dense filter effect along with a wide range of stops. Pretty happy overall and I'm pretty sure this will be a main driver during the summer.

I upgraded to this K&F VND2-2000 from my K&F VND2-400. This gives me more versatility when I need to get that light stopped down. Weather I'm shooting waterfalls and need long exposure or I'm shooting slow motion and need to stop the light down to keep my shutter consistent, the extra ND is perfect. I'm a fan of K&F their filters are very affordable and the image quality is still quite clear. The build quality and tolerances are quite nice.

This variable ND filter by K&F Concept is really well made. The threads and fit are perfect and the optical quality is better than I would expect at this price point. I like the convenience that a variable ND filter provides and this one has enough of a range to meet all of my needs. There are no hard stops on the setting, but the rings are stiff enough to stay where I set it and I don't have to worry about accidentally changing the setting if I bump it. As with other K&F Concept products, the included individually packaged cleaning cloths are also a nice addition. Overall, I'm very happy with this filter.

I shoot a lot of video with different lenses, and lately have been using my 24 f1.4 Sony lens quite a bit while outdoors, and this can be a very bright lens, so using a variable ND filter like this one by K&F can definitely be useful and a big help to shoot with low apertures and further blur out my backgrounds nicely. I didn't notice any real color shifting, and my image has remained sharp as expected. I like that this one is so variable and allows me to use just this one filter, rather than having to keep changing them out to different ones and the light changes. It's just more useful. I'm thankful this one came with that little plastic storage case, rather than a pouch or something useless, because it helps me to protect the filter when not in use. This is a nice inexpensive alternative to much more expensive ND filters and it's actually quite nicely made.