Admittedly, the system of magnetic filters is not entirely new and I can't say who has copied from whom here, but K&F is already known to me through very good lens adapters and solid tripods. I was of course interested to hear that K&F now also offer such a system.
Whether the magnetic K&F round filters could convince me or the low price demands too many sacrifices, you can read in my review...
So far I have used screw-in filters from Rodenstock, B+W, Heliopan and Haida. These are all brands where a filter tends to cost what K&F wants for a complete set including a bag. I was therefore very sceptical about what to expect, also because K&F advertises Schott glass (hardened and therefore very robust) and 16-fold nano sealing. That reads amazingly well, but in practice it doesn't necessarily mean anything, because in the end it always comes down to optical performance, no matter how great the handling advantages are.
The set contains in each case...

- a very delicate adapter ring to screw in
- a UV or protective filter (to protect the front lens)
- a CPL polarising filter (removes reflections and enhances contrasts)
- an ND 1000 filter (darkening for longer exposure times. Water becomes silky, clouds blur)
- a storage bag
the filters, their workmanship and feel, is great. There are no visible defects, the threads of the adapter ring and UV filter run silky smooth, the holding force of the magnets is just right and even the fine knurling of the edge is perfectly finished. If it didn't say K&F on it, I wouldn't be able to distinguish the filters from any of the branded filters in my portfolio, purely from the outside
I don't know how K&F managed to do this at this price.
The most time-consuming part is opening the bag, the rest, well, "snap" and the filter is changed. The magnet has so much power that even if I attach the lens cap, there is no danger of anything coming loose at any time or in any position!
The whole thing is so ingenious that I ask myself why someone didn't think of it much earlier. Gone is the fiddling with unscrewing and how often I used to be annoyed that the filter is difficult to put back down again