as described
I bought a tower to cool an old booster pc with a passively cooled graphics card that tended to get a little too hot.
So I made a few holes on the side of the tower and added a ventillo that I had on hand.
But to avoid cleaning too often I took a small filter.
The only problem is that the magnet is a bit limited, it holds but it's only because of the screws of the ventillo which are 1 or 2 millimetres bigger than the magnet.