The ND filter set for the GoPro Hero 9 - Hero 11 was well packaged and delivered quickly. The four ND filters supplied should also function as polarizing filters. You can achieve great results with these filters. You capture more details, especially on sunny days. But the filters are also ideal for water shots or similar, as they eliminate metallic reflections. I could also see this in my test shots. I had a similar experience with the ND filters. These are like a kind of sunglasses for the camera; the higher the value, the darker the image. If you are filming at 4K 30fps, the shutter speed should be 1/60 to make the shots look cinematic. But this is impossible on sunny days, even if the ISO is 100. So you need an ND filter to darken the image. If you want to record at 60fps, you should set the exposure time to 1/120. For this you need an ND filter with a small value. So far I have only used the ND8 and, on very sunny days, the ND16 filter. The other filters are only suitable for special applications or for long exposures.
I am also satisfied with the quality of the filters. They are made of aluminum and glass and are very light. The filters can also be attached and removed without any problems. They also sit very firmly on the camera.
In the end, you get inexpensive ND filters with an integrated polarizing filter that help you record the video with the ideal exposure time.