The PT-AF14-3B washable air filters are originally designed for Lian Li PC cases as a spare part but can also be used for other manufacturers' 140mm retail fans. The PT-AF14-3B Washable Fan Filter fits between the fan hole and your intake/exhaust fan to make sure only clean air gets pulled through your case. Every couple months or so, you can pull out the filter and wash it, keeping it effective. 100% washable and easy to use! 2pcs/packing.