KW801/802RG KleenWater replacement O-rings compatible with Cuno Aqua-Pure AP801/AP802 housings, Set of 2 A high quality, low cost alternative to more expensive OEM o-rings For a (3) cartridge kit with (1) o-ring Amazon Search KW810EC(3)-AP801oring(1) (2) Replacement O-rings compatible with KemFlo FM5000 & FM10000 series water filters (2) Replacement O-rings compatible with Keystone CG10 Two KW801/802RG KleenWater Filter Housing Replacement O-Rings Compatible with Cuno Aqua-Pure AP801 / AP802. We recommend consumers keep a spare o-ring on hand to avoid urgent situations. This o-ring will accommodate filter housings which require large diameter cartridges. For filters which have an approximate diameter of 4.5 inches. The o-ring itself actually measures approximately 5 5/8 inch (inside diameter). An o-ring facilitates a water tight seal between the water filter sump and the water filter head. The most common o-rings used in water filtration are made from Buna N material. Buna N is also commonly referred to as nitrile. This is the ideal choice for cold water filtration because they are inexpensive and have superior performance characteristics. This o-ring is a round bead shape. If you require the square cut version compatible with 3M Aqua-Pure model 68898-31 please enter KW108(3)-Holders(2) in the Amazon search bar.