Review on SilverStone Technology SST-FF81 SST-FF81B 80mm Fine Fan Filter with Magnet Cooling - Black by George Scoles

You need it. If you read reviews of these things, then yes, you need them. Anyone with PC fans, let alone a high-end PC like mine, needs them wherever there are air intakes, including a fan for your PSU if you've run one into your case! I have an extremely dusty apartment and that makes a big difference. I clean them every week because it takes so long for them to get clogged with dust. Your mileage may vary. If they aren't flush-fitted, ie they crease somewhere around the edges (which keeps air from being sucked through the mesh). I have found that some type of tape seals the gap neatly and allows all air to flow through the mesh. Filter. I suspect my fit issue is that I actually mount them on my case through my heatsink, opposite the fans which are mounted on the inside.