O-Rings for Pentek PBH Housings:

O-rings can be replaced for wear and tear reasons or to allow for different materials to be chosen for compatibility issues. These are used between the head and the sump.

Liff Replacement O Ring Seal for NP1, NDL2 water filter housings and RLK, RBK double filter housing (x2 for needed RBK)

O ring seal 86mm diameter x 3.5mm Thickness

also fit many other imperial 2.5 x 10 inch housing.