Thermaltake Matric Due 2 Sizes of Magnetic Fan Filter AC-004-ON1NAN-A1 FINE FILTER for DUST REDUCTION - Super fine mesh with excellent protection and reduction against dirt and dust, allowing more air through the filter while stopping the dust. MAGNETIC FRAME - Fitted over the fan intake or vent holes on PC case using magnetic strips built into the filter. SCREW HOLES READY - Four reserved screw holes at each corner for mounting to non-metallic surface. GREAT RELIABILITY with PSU - Designed to prevent dust from entering into the PC system, as well as idealing for PSU air intake grill, improving reliability and reducing dust prevention. TWO-SIZE COMBO - 2 sizes included. One for 120mm fan; while the other one for 140mm fan or vents.