Here's a short review of my experience with the "K&F Concept B-Series Motion Blur Filter-2".

It arrived securely packaged in a product box and a storage bag.

The 100mm version makes a high-quality and professional impression right away.

For my test, I used a small telephoto zoom lens with a tripod base, allowing the filter to be attached to the lens using a "magic arm". This allows for more consistent results than holding the filter in front of the lens by hand.

I experimented a bit with the filter in various lighting conditions and was quickly able to achieve some usable results in both still life and portrait photography. This makes it easy to add some playful effects to photos.

Of course, you could also generate and incorporate such effects into your photos using Photoshop (or alternative photo editing tools) or AI. But as a photographer, I enjoy the results I can achieve by incorporating these kinds of creative tools directly into my photos, without having to sit down at the computer afterward. Maybe I'm a bit old-school, but that's precisely what makes photography so appealing. ;)

Here's a photo—unedited—straight from the camera, taken with the effect filter.

In conclusion: Good filters come at a price, and the K&F Concept filters aren't cheap. However, anyone who still enjoys the physics involved in photography can have a lot of fun with this filter set. I still find the nearly €40 price tag a bit steep, though, since the 100mm set would cost me almost €160. That would be a bit too much for me. I'll wait and see how the price develops and whether I end up buying more...