The K&F Concept Circular Polarizer and Neutral Density Filter offers the convenience of two quality useful filters in one, at a reasonable price.

The neutral density filter provides between 2 to 6 stops of light reduction, more than enough when wanting to slow your shutter speed for video or specific type of photography, like waterfalls.
Similarly, the circular polarizer removes glare and enhances color and contrast.

Although the filter did not come with instructions, using it is easy, and the outer rim of the filter is clearly marked to indicate the amount of light reduction. Turning clockwise changes ND levels, and counter clockwise is the circular polarizer.

The rotation of both the ND filter and circular polarizer is smooth and even, and the frame, which is made of aluminum alloy, is well-machined and screws easily into the lens. Overall, the filter appears very well made and it even comes in a very nice (leather looking) carrying case.

Bottom line, this is a very useful and convenient filter to have in your kit. Content creators of all types, video and photos, will appreciate the ability to reduce light for video and different types of photography, and increase contrast and color vibrancy.

Highly recommended!

Really nice 2 in 1 variable ND and CPL filter. The inclusion of the two putters makes it exceptionally easy to make adjustments one way or the other, depending on what you're adjusting. Turning the filter clockwise changes the density between ND4-64, while turning the filter counterclockwise adjusts the polarizer effect.

I find the 6 stops between ND4 and 64 to provide a very versatile range that works for 99% of the things I'm shooting. The adjustment is smooth, and the density changes evenly and consistently throughout the entire field of view.

The polarizer adds much needed functionality and eliminates the need to stack an additional CPL on to the ND filter.

I experienced no color shift or vignetting while using the filter.

Filter comes with a nice storage case as well.

This is the variable ND filter and polarizer.
The CPL filter eliminates light reflections on surfaces, cars, water, glass, and also enhances the colors of the sky, leaves, asphalt, etc.

I personally use it for video so I don't lose depth of field by closing the aperture (from f9 I can now go to f2.3 without burning the images due to too much light).

About the image quality. Well, excellent: There are no dominants, no chromatic aberration, no loss of sharpness or the horrible X of gradual ND filters.
I have a very expensive polarizing filter and hardly notice the difference with this one.

Price and performance are top !!!

This is a high quality circular polarizer variable neutral density combination filter from K&F. I used the 77mm to cover most of my lenses using step up rings. The smallest filter size is 52mm as shown in the photo. The filter is excellent for everything it does and it is inexpensive. It's much more convenient than separate filters; it is quicker to use and requires less carrying in your pocket. This also works for some wide angles, which would be a problem when stacking multiple filters. The build quality of the filter is excellent. A leather storage case is included. From 4 stops onwards there is a slight vignetting and color shift, which increases with increasing ND filtering. This is expected and can be fixed in post-processing if desired. Image sharpness and sharpness are not affected. This filter outperforms other CPL+ND filters I have used.

I tried using the variable ND filters on the DJI Osmo Pocket 3, but found them too fidly. Instead I went for this 4 filter kit which works great. AND BONUS: You can stack these filters on top of each other! You can even stack the polarizer on top of the ND filters. PLUS the other thing I like about the K&F concept filters is, they have little indents on the side that you can get your fingernails into to place the filters on the lens and it also makes it easier to remove the filters as well. I tried the other brands, which are good, but they don't have these little finger nail indents. PLUS the camera can rotate the lens to the closed position with the filter on (However, it will not close with stacked filters on—>just one filter on)

Very good quality The combination of an ND filter and a polarizer is very practical in practice as it avoids having to use two filters at the same time. The optical quality is first class, no crosses.

It is a variable ND filter and polarizer. The CPL filter eliminates light reflections on surfaces, cars, water, glass, and also enhances the colors of the sky, leaves, asphalt, etc. Personally, I use it for video so as not to lose depth of field by closing the aperture (from f9 can I can now go to f2.3 without the images burning due to too much light). About the picture quality. Well, excellent: there are no dominants, no chromatic aberration, no loss of sharpness or the terrible X of Gradual ND filters. I have a very expensive polarizing filter and I hardly notice the difference to this one. Price and performance are great!

This is a good kit if you need a filter system that includes ND and polarizer. Image quality is not degraded with the included filters. The filter holder is sturdy and easy to install.