AP810 and Keystone CG10 Compatible Replacement Water Filter Cartridges, Poly-Spun, 4.5 x 10 Inch (3) with O-Ring for AP801 by KleenWater Water filter housing replacement O-ring for 3M Cuno AquaPure AP801 and Keystone CG10 by KleenWater Three graded density 5 micron polypropylene 4.5 x 10 inch sediment cartridges with grooved surface FREE SHIPPING. A high quality alternative to the expensive OEM cartridges The universal cartridge dimension insures compatibility with all 4.5" X 9.75" housings It is important to have an spare o ring to avoid an urgent situation