The Everpure EV309709 R is a compatible replacement O-ring for the following filter housings:
The Everpure EV309709 - Comp. Filter Housing O-Ring fits several water filter housings from Culligan, Ametek, Pentek, US Filter, Plymouth, Kleen Plus, and American Plumber. This buna O-ring measures 5 3/4" in diameter and has a bead size of 0.17". This compatible Everpure O-ring is used in all Big Blue housings by Pentek with 1" and 1 1/2" inner/outer diameters (except for the Big Clear Housing).