R & S #238 / Food Grade And Drinking Water Grade FDA NSF61 / 63597-174C / OR006 ? WP252235 O-Ring for Housings:AP11S, AP11T, AP12S, AP12T, AP26T, AP51T, AP101S, AP101T, AP102S, AP102T AP110Watts 500222, 500223 Waterway 805-0238 SVL56 Diffuser O-Ring Tailpiece WhisperFlo WFE PumpPurwater FHT-34, FHO-34, ORG006Omni Filter OB5 Made In USA Complete Return Policy O-Ring problems: Send us your old O-Ring that worked and we will find you the proper O-Ring.