GT3 & GTX Series filters: used to “pre-filter” the ink prior to entering the printhead.  They must be changed during regular recommended maintenance, to avoid print quality issues. These filters can NOT be cleaned by flushing them with cleaner.  They must be replaced as needed, or during regular scheduled preventative maintenance. Be sure to install the filter in the correct direction, per the gallery image. Two different filters are available for use in the GT-3 Series Printers: GT3LCF121 LCF Filter Disc #10 is for CMYK (Colors) GT3LCF131 LCF Filter Disc #20 is for W (White)