I tried this filter on my Sigma 17-50 and the result is really amazing. The product looks great in its really high quality packaging and is easy to carry in your pocket. The photographic rendering is of a high standard for a low price. I find the tongue very interesting, it allows a better grip at work.

Great filter glass is clear and it does it's job well. No complaints at all

I’m new to photography but this filter has really helped make take new photos I couldn’t before ok slow shutter speeds, the delivery was very quick and delivered safely

As always, delivery was fast and on time. The package includes a stylish protective bag that protects the filter from dust and scratches.
I mainly use the variable gray filter for videography to keep time and aperture constant. The adjustment of the filter is smooth, not too difficult and not too easy; unintentional adjustment is hardly possible. The X that results from variable filters is only slightly visible at the highest level (ND9) and will hardly come into play with videos. I don't use Var for photos anyway. neutral density filter.
Completely adequate for my requirements and therefore recommended.

I bought this for my iPhone, and never found an adapter with decent enough ratings to buy yet. However, while holding it in place as I take pictures of record some video footage, it is actually surprisingly good. I'm not sure if the same experience would translate to a Camera, but overall seems like a pretty good product.

I got to try this filter for my Sigma 17-50, and the result is really amazing. The product looks great in its really great quality packaging and easy to carry in your bag.
The photographic performance is at a high level at a low price. I find the tongue very interesting, it allows you to have better grip during work.

You can feel some vignette, in this filter it is from half to max. Everything else, like the picture quality, sharpness, fits the lense etc, is really good. It is'nt bad for the value of this amount money!

I purchased the K&F Concept Variable ND Filter Neutral Density ND2-ND400 (9 stops) with Rotating Ring to be able to use a fast ND with different densities.
The packaging is very well done, solid and space-saving container. The glass filter is light and the ring to increase/decrease the density is smooth. It has no end stop lock.

To test it best I tried it with three different lenses on the Nikon D750 camera (full frame): 20mm, 35mm and 85mm.
- 20mm: in the photos taken with the filter there is no particular loss of sharpness, it introduces a slight hot dominant that can be easily solved in post-production. As far as the X-shape problem is concerned, it is quite marked using the filter beyond the marked ring. Instead, using it within the marked marking, the problem is little present. See image attached.
- 35mm: in the photos taken with the filter there is no particular loss of sharpness, it introduces a slight hot dominant that can be easily solved in post-production. As far as the problem is concerned, X-shape is not as marked as in the previous one, but there is a vignetting especially in the use with maximum effect. See image attached.
- 85mm: in the photos taken with the filter there is no particular loss of sharpness, it introduces a slight hot dominant that can be easily solved in post-production. As far as the X-shape and vignetting problem are concerned, they are not relevant. See image attached.

Optically, the filter is well made and provides excellent results, but I would have preferred a start and end run with lock in order to avoid possible mistakes. Also considering that K&F produces other types of filters but with magnetic connection, I think it could be a further plus for this filter.

The price/performance ratio is correct based on the performance provided.

I attach more photos of the packaging and two shots to the sea.

The handle to change the filter level is easy, the filtering itself looks great and enables perfect recording without changing the filter. We went on a trip this weekend and that filter never left the lens. If you are shooting outdoors, do yourself a favor and record this. No fiddling with filters in your pocket. Just dial in and off you go.

I was surprised by the quality of the filter which is professional and has nothing to say. The materials are good and the glass is great too. The adjustment wheel is very smooth, so you can easily change the density of the filter. You no longer need 4 different filters. Ability to record videos during the largest opening time of the day.