The K&F Concept 82mm Linear Mirage Pentaprism Filter:

The first BIG surprise about this filter is... yes, it's thick. And heavy. A lot of glass for the money - and a lot of fun!

Technically speaking, it's a sheet of glass about one centimeter thick, half of which is smooth and then slopes down at an angle - with four edges that each act like flat prisms. The effect: one half of the subject remains as it is, while the other half is refracted and thus duplicated. To make the effect controllable, the filter can be rotated like an ND or CP.
The effect is initially difficult to judge in the viewfinder/on the display; it certainly requires some practice.
Speaking of practice: the filter itself is easy to grasp, but its application and possible effects are a matter of trial and error. This is definitely a filter that begs to be taken out and tried out.

In my opinion, like similarly constructed effect filters, it works best with high-contrast subjects and strong lights (traffic, nighttime). Personally, I wouldn't use it as a portrait filter—it's not my style. However, I see real strengths, especially for night shots (unfortunately, I couldn't take it due to the persistent rain over Pentecost).
I took a few photos with it, which hopefully show the effect clearly.

The filter is also quite interesting for video (see short example). However, since it protrudes far, it is likely to produce strong flaring—which can be very exciting.

Conclusion: Very good workmanship; I can't detect any aberrations.
A creative toy worth exploring. I'm looking forward to it!