Keep your spa water clean and Intex Purespa performing at its best by using genuine Intex Purespa type S1 pool filter cartridges. This package includes 8 filter cartridges. This is the authentic replacement cartridge for your Intex Purespa. Replace your filter cartridges regularly for the best results. It is recommended that you replace cartridges every 2 weeks to maximize your spa's performance. Help ensure the longevity of your Intex Purespa by regularly choosing Intex Purespa type S1 pool filter cartridges.