If you shoot photo (or specifically video) outdoors in the sunlight, you NEED a variable ND filter.

For video, if you're shooting 30 FPS, you need to keep your shutter speed at 1/60 (because of the 180 rule) for natural blur and smoothness. If you want a nice blurry background at f/2.8, even at ISO 100, there's a great chance your image will be horribly exposed. Your only options are to increase the shutter speed (and compromise the natural look with distracting "choppiness") or crank up to f/16, which will flatten your image and get rid of that blurry background you wanted!

In comes the variable ND filter. When applied, like variable sunglasses, it allows how much light passes through, kind of like an intimidating bouncer at a night club. So just twist the ring on the filter and you can achieve your shot perfectly!

With this specific filter, two small things bummed me out:
1. The ring doesn't have actual stops, just continuous rotation so you can't really keep track of the specific amount of light you're letting in.
2. When the filter is on my Tamron 28-75 2.8 lens, I can't put the lens cap on at the same time. Not a deal breaker, but annoying when you want to quickly take a picture or shoot some video.

But for the price, it's hard to argue this isn't a great purchase.

Bought this in combination to be used with my Sirui 50mm Anamorphic lens. It works well and I don't too much chromatic aberrations. The color rendition is nice and it definitely allows me to keep my aperture wide open at 1.8 during bright conditions. The Sirui 50mm Anamorphic lens is quite sharp wide open, and using the variable ND with this lens creates magic.
I definitely recommend this lens for ANYONE that needs a quality ND filter for their lenses. I wish it came with a lens cap - or at least a universal one. The original lens cap, doesn't quite fit in this filter.

Very easy to use, looks very good material. I love the result. Playing with the white balance you can get much better result. I have tested with ISO 100 f / 1.8 and 1/125 sec. when the sun does not let see anything in the camera, and this has allowed me to put it totally dark and also in a desired tone.

Long exposure. At first I hardly used it, now I'm a huge fan. I shopped around and found the perfect tripod (carbon-fiber Manfrotto, also great). When that arrived, I mentioned to my friend I was planning on getting waterfalls with a slow shutter speed, and he said, "You gotta ND filter, right?" I knew I had a trip up to Letchworth coming up that weekend. That evening I rushed onto Amazon, shopped around, and found this product. Perfect size for my Zeiss 50mm and 35mm!

I didn't really get the chance to mess with this ND filter until I arrived at Letchworth and wow was I blown away! The crisp rolling ring and the crisp shade of black make this such an incredible product. So worth the price! I'm blown away by how it doesn't degrade the quality of my captures my lenses can get.

I love long exposure now. With my lightweight tripod and my filter, I can only grow.

I included a picture of a covered bridge in Cuyahoga Valley National Park taken with this filter. It was a eight second shutter speed.

This is a product I chose after reading the reviews. It is highly recommended for starter photographer. The adjustable feature is definitely.
I have taken multiple photos with and without the filter, and will different settings on the filter, and I can see the improvements in the results.

I had a smaller diameter of this product for a different lens, so when I got my new lens the first thing I bought was this ND filter. It is incredible. And this one had little dots along the edge, as well as text that read "Min" and "Max". This was super helpful. My only complaint about the smaller ones was that you couldn't tell how far was the maximum and minimum, and this model has solved that issue. I don't go anywhere without this filter. I will be buying a K&F Variable ND filter for every lens that I get from now on.

Good build quality, but I would prefer to have smoother and easier turning. It is a little stiff. For the money the build quality is good. Image quality is good, just make sure to use the filter in the intended range shown on the markings. Heavy vignetting begins to appear on the last dot (darkest setting) and beyond that you can see the infamous X-pattern. Going to the lighter end, I see no vignetting at all. I use this between the brightest dot, and second-darkest dot. There is a yellowish colour cast that is present in the entire frame, thankfully no colour splotches that are difficult to fix. There is no colour shift when you move the ring. My biggest inconvenience is just that the filter thread on the front of the filter is slightly larger than my lens' filter thread, which means I can't put my lens cap on the filter. On my fuji XF16-80mm, the lens hood will not fit when the filter is on.Overall it does the job pretty well in most situations (overcast, indoors, golden hour, etc) , except in direct sunlight (at noon) you will have to stop down your aperture to maintain a 1/48th shutter speed. Some inconveniences but many of them can be worked around. You get what you pay for at this price.

Good quality. I would buy it again.

This item is worth buying for the price, I tried it out and it seems to be working fine.

For me this filter fulfills its purpose and it is currently the best filter at this price