I'll be honest using ND filter can be tricky since you're glass in front of glass. However KF concept is really creating spectacular items. As this ND filter allows for me to use my 50 1.2 wide open outside while keep the background smooth and blurry. The red knobs aid in adjusting the smooth ND strength ring and allows you to have a tactical sense of where the ND is bases on positioning. The quality thought the filter seems excellent with minimal impact to the image quality.

I am familiar with ND and polarizer filters but have never seen a single filter combining both. I took a chance on it, thought I was wondering how the filter could work to use both filters but still control them individually. They have a clever system for this.

This is how it works:
The filter screws onto the end of the lens as usual. To control the polarization, turn the lens counter clockwise (from the position of holding the camera with the lens pointed at the subject) until the reflections or glare get cancelled out. This direction of turning fully counterclockwise sets the Neutral Density reduction at the minimum level. Then to control the ND, turn the filter clockwise. The ND amount increases from the filters minimum to the maximum within a range of about 1/6 of a rotation, and a resistance can be felt which is reaches the end of the range, but if continuing to turn clockwise the ND filter stays dark which the circular polarizer turns, allowing to have both the ND and polarizing at the same time. Or the filter can just be for polarizing with only a the minimal degree of ND (1 stop of light). Basically the polarizing filter is always "on" but because of the nature of how the effect is only visible at a relevant rotation for the seen, it is not hard to get a photo without the effect. Note: the polarizer can introduce some color shift as well as hiding reflections.

I got this for a lens that fits on a DSLR camera, but it also works if it is handheld in front of a cell phone lens.

AL ser ND "oscurece" según las necesidades, muy útil aquí en el Sur que el sol pega bien fuerte. El filtro polarizador, funciona muy bien, para muestra un botón.

Un filtre toujours de qualité, très pratique d’utilisation sur mon objectif.
A savoir, mais cela ne peut en être autrement, l’impossibilité d’adjoindre le pare soleil.

High quality, but lack of lens cap.

Excelente producto, cumplió con mis expectativas

I've had a favorable experience with K&F products, particularly the Concept line of filters, so you'll find a lot of their products in my camera bag (which is also a K&F product). This filter provides a limited amount of light reduction (with 5 stops of range) with a circular polarizer in one filter. I use several Canon lenses on my Canon mirrorless bodies that all use 77mm filters. This "two in one" K&F filter is a convenient to get the benefits of ND filters and a circular polarizing filter without stacking two filters. In my experience both elements (polarizing and light reduction) work well without little or no image quality reduction. The ND range is limited, but if you're outdoors in very bright light, you can go to a ND filter with more stops of light reduction if needed. The circular polarizing function worked well with no visible "x cross." Recommended.

This Camera Filter helps me nail the dark, moody photos I’m always chasing. It adds that perfect touch of depth and atmosphere with minimal effort, turning otherwise mundane shots into something much more dramatic. If I’m looking for a quick way to enhance those shadowy vibes without fiddling too much with settings, this filter does the job.
That said, I could achieve pretty much the same effect by tweaking the camera settings directly, making the filter feel a little redundant. It’s nice to have for convenience, but it’s not exactly a game-changer for anyone already comfortable with manual adjustments.

I don't do a ton of video work but I really want to. This includes both a circular polarizer to cut down on reflections (perfect for ensuring that folks with glasses don't have bright reflections. A variable ND filter to cut down on bright scenes and ensure that you can get optimal shutter angle.

The build quality on this is fantastic and the quick throw levers on either side allow you to make adjustments to the filter quickly and precisely without having to risk smudges on the front of the filters.

This is a great variable ND filter from one of the most trusted camera accessory brands, so my expectations were met completely.

The clarity is top-notch, without any visible color or image distortion, and it doesn't suffer from the X Cross image distortion that many low priced Variable ND filters exhibit.

The filter is easy to adjust, thanks to the easy access handles on the sides.

One word of advice. If you have multiple lenses with different diameters, I suggest you order one at the highest lens size you'll use, then get inexpensive adapters to put the larger filter on your smaller lenses. You need to know that you should not try to adapt your larger lenses to use smaller filters.

The bottom line is that you can easily put larger filters on smaller lenses but putting smaller filters on larger lenses will cut off part of your images.