This is the base for the 90-pleat filter cartridge. You don't need one for every filter cartridge, but some customers forget to remove them from the cartridge when they throw the old filter cartridge out. We will be discontinuing this stock unit when all of the 90 pleat filter cartridges have sold, as we switch to the 120 pleat filter cartridges for all spas.

PART-B9301402

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