Review on ThreeBulls 12 Pcs 120mm PVC Black PC Cooler Fan Dust Filter Dustproof Case Cover Computer Mesh - Keep Your Computer Dust-Free and Efficient by Mike Calderon

What's not to like about that? Despite being very thin, these things are really effective at collecting dust. Keep in mind that they restrict airflow very little, but anything you put in front of the fan will do. Just make sure those filters are clean! Just take out the filter and blow out the dust with compressed air and replace it. You can also wash off the dust with warm water. I do not recommend using soap, plain water will do. Just let them dry before putting them back in. They get the job done and are worth the investment.