The Super-Pro O-108-9 is a Tagelus/Triton II/WhisperFlo® Lid O-Ring for use with models made before 11/1998. An O-ring is a round mechanical gasket used in static or dynamic applications. O-Rings block paths that allow liquid or gas to escape. For pool and spa applications use your O-Ring to secure pool pumps, filters, valves and piping.