These K&F Concept filters are spot on.
They are really nicely made and come in a nice little protective case.
You'll know what ND filters are for if you're looking at them, but if you don't just think of them as sunglasses for your camera.
You get ND8, 12, 32 and 64 so you get equivalent f stop reduction of 3,4,5 and 6 stops.

When using the action cam in sunshine on holiday, not often in the UK :) it can help colours look cleaner and reduce glare etc.

They screw on and off the action cam really nicely.

I'm unsure as to the waterproofing side of things but I assume they'll be fine. I just put the original on when I'm in the water just so I know my warranty is covered.

These filters surprised me: low price, no noticeable loss of quality and ND together with adjustable polarizer, all in a sturdy and small-sized box, K&F concept is no joke.

I have both the GoPro 11 and the DJI Osmo Action 4 cameras, as well as the DJI Mini 3 Pro drone. I use ND filters for all of them and the drone ones also come from K&F Concept. I'm very happy with them.

The really cool thing here is that these are both ND and PL filters. Why? Because if you have them as separate filters, there's no way to use them together.
If you're looking to get these, you're probably aware what ND/PL filters are. But there's a small chance you may just be exploring various available accessories for your new camera. So ND filters will help in that really sunny weather, where your camera sensor gets too much light and the picture looks overexposed. It blocks an amount of light depending on which filter you use. The result is better contrast and richer colors. The PL filter further enhances it by removing unnecessary glare. Now glare can be found in more than just the surface of water. It can be a glass or metal object, snow or even…leaves. Just look at the video.
The filters are really well made. The glass looks and feels strong and solid, the threads fit perfectly and the whole thing looks really professional. The PL filter can be regulated by twisting the ring.
I like the storage box. It's hard plastic with some nice foam cuttings. The filters are easy to take out and well protected from damage.
The weather wasn't good enough when I filmed the video, but at least I had some sunshine. Summer's gone - what can you do? The difference the PL filter was making can be clearly observed though.

I've seen loads of videos where people don't utilize these filters enough. It's a quick operation to swap them (much quicker than on the drone!), so I'll have them with me everywhere.

Thank you for reading my review. I hope you found it helpful.

No complaints on the Action 5. These aren't too hard to press on to the lens and hold strong enough to not get knocked off. The cleaning cloth is appreciated since fingerprints seem to be a required part of the installation process. Other than the polarizing and darkening I didn't notice any impacts to image quality but I'm not pixel peeping when using an action cam. These fit even with the case on the camera.

I'm new to using ND filters for lenses. An Neutral Density (ND) filters reduce the intensity of all wavelengths, or colours, of light equally from entering the camera, in measured amounts.

The four pack lens comes in it's own plastic carrying case. Designed for DJI Osmo Action 4 they clip onto the existing lens.

The glass lenses are great quality and is a great price.

This set of six "push on" filters fits over the lens of my DJI Action Pro 5 snugly. It takes some effort to push them on (and pull off). They won't accidentally come off. They come packaged in a flat (0.75" thick), but relatively large (6.25"x6.25") plastic & fitted foam case. This case is too large to fit inside any of my "action cam hard cases" as is, but you could re-package the lenses if you found a suitable "accordion fold" style holder.My DJI action 5 pro does a relatively good job changing the shutter speed to accommodate a wide variety of lighting conditions, and because of this the videos with the various ND filters look somewhat similar to each other. (Longer shutter times as you get up to the higher ND numbers may introduce motion blur where you wouldn't normally have it.)There is a visible difference between the normal lens without a filter, and with the polarizing filter attached. But just having played with them casually, I haven't found a use case where the filters are actually necessary for my Action 5pro to delivery good videos. So if you like to have options, or have a specific need for a ND or PL filter, they are nice to have on hand, but if you are trying to decide if you need them.....you probably don't.

This polarising lens arrived in a shrink wrapped cardboard box. Inside, the lens is in is own plastic storage case with a custom foam insert.

It screwed onto my Osmo 4 Action perfectly. The polarising lens rotates smoothly with just enough resistance (see video).

To test this I took a couple of pictures of our garden pond. The reduction in the reflections from the water is obvious but what most impressed me was the way it removed the glare of light being reflected from the leaves of the plants to the left of the water (see pictures).

This is a good polarising lens that fits the Osmo 4 action perfectly and performs well.

Great filters but my only gripe is the case. It would be much nicer to have them stacked in a log shaped case as opposed to a large flat case that’s just big and awkward in my camera bag… otherwise no complaints.

The product does what it's supposed to do. It makes the image look much more vivid and better. Thanks to the simple installation, the lens is installed in just a few moments, which I personally really like. It also holds very strong so it can't fall off

Nice looking PL filter, and it's been a treat for outdoor filming. It's a 4 PL filter that effectively reduces glare from non-metallic surfaces. Crafted with high-grade AGC optical glass, it ensures exceptional clarity and minimal distortion.

The standout feature is its 28-layer multi-coating technology, K&F Concept have rarely disappointed when it comes to photography equipment and their filters are no exception. This filter significantly reduces reflections and glare in challenging lighting conditions. It's particularly effective on water reflective surfaces.