Hydronix SDC-45-1020 10 x 4.5 Inch 20 Micron Whole House Sediment Water Filter Cartridge - 6 Pack 20 micron sediment filter for cleaner water Graded density for higher dirt holding capacity For optimum dirt-holding, replace about every 2-3 months Materials ANSI/NSF Standard 42 tested and certified Fits most Big Blue housings that accept 10-inch x 4.5-inch water filter cartridges