dust filter 2x40mm, square - black/white demciflex computer and electronic dust filters fits over the air intakes of your electronic or computer equipment by way of a built-in magnetic frame. it was designed to fit on the outside of the case and needs no screws, tools or special skills. the design allows everybody to use it no matter what their skill level. no need to open the case or undo anything at all. the intake vents we refer to are the grills or ventilation holes in your computer's case where cooling air enters the case. some of these vents mayâ¦