However, a disadvantage have the filter for me: If the holes for the screws facing down so that they -lassen- obstruct, the grid is curved downwards which means that the filter sand on the fan, make a lot of noise and certainly nciht good for the fans are!
Fixed the problem I have, as I've just bent the grating on the sides upwards to reverse the curvature. The fan filters are working properly and keep the dust back well.
I recommend anyone who has 'exactly Matching screws' for his fans, the grid to bend outwards so that there are no complications.