Magnets don't stick to aluminium though...
but....
Demciflex filters come with a self adhesive magnetic ring which you stick to the case. The magnetic filter then sticks to this. I have one on the wifes pc and it works a treat.
Indeed. I have mounted the magnets on the inside of the case and and the mesh on the outside for a cleaner look. Or all on the inside for super stealth. They really are very good.