O-Rings compatible with KleenWater PWFHT4510BT, PWFHT4510BR, Atlas Dp big and YTB, Set of 6 Inside diameter 5.475 inches High quality Nitrile Buna material 6 Pack - Great Value 6 Replacement o-rings for model KleenWater KW4510BT, KW4520BT, KW4520CBDS and PWF4520LRDS. This o-ring will accommodate filter housings which require large diameter cartridges. These cartridges have an approximate diameter of 4.5 inches. The o-ring itself actually measures approximately 5.475 inches (inside diameter). Please be advised that this o-ring is compatible with the KleenWater, Atlas DP Big and YTB brands. We recommend consumers keep a spare o-ring on hand to avoid urgent situations.