These little round files are fantastic for smoothing and shaping slots, but they are easy to bend if you are too forceful, but they can also cut into the nut surprisingly fast as well so it's easy to go too far if you aren't careful.
They are great if you work gently and take time to stop and check your progress.
I don't think I'd try to cut a new nut with these as they are too flimsy, but for smoothing and shaping existing slots and sharp edges they are excellent.
For the price this is a no-brainer addition to your workshop.