This Diffuser O-Ring is for use with the following pump series and models: EcoStar SP3400VSP, TriStar VS SP3200VSP, TriStar SP3200EE and SP3200X, and NorthStar SP4000 and SP4000X. An O-Ring is a simple, yet essential sealing component designed to prevent leaks and maintain consistent pressure in a wide range of mechanical, plumbing, pool, and industrial applications. Installed in a groove and compressed between two mating surfaces, it creates a reliable, tight seal that blocks the passage of liquids and gases. It withstands repeated compression, vibration, and temperature changes.