For ND filters (without gradient) the concept seems very conclusive to me. Incidentally, the additional ring can also be used to attach another lens to the magnetic connection. The magnetic force seems strong enough to me, it's actually not that easy to remove the filter without shaking the camera. You definitely don't have to be afraid that the filter will fall off at the most inopportune moment. The image quality does not suffer visibly from the filter, as far as I was able to judge tonight. Because dusk was already setting in, I was only able to achieve the same brightness relatively soon with an increased ISO (no tripod with me...), which of course led to losses, but these have nothing to do with the glass as such. the first pictures, that could still be shot with different exposure times did not show any significant losses even in the 100% view. However, there is a slight discoloration of the image, which turns purple with the filter. (Supplement a day later: in daylight and light snow, the picture with the filter was harmoniously balanced overall (trick: no strong contrasts...) and therefore significantly "warmer" than without the filter)