Pack of 24 genuine Intex Type S1 filter cartridges The S1 Cartridge Filter is sure to keep your PureSpa Jet Massage water clean and fresh Made with easy to clean, heavy duty Dacron paper for the ultimate filtration For maximum efficiency, clean cartridges each week and replace once a month or sooner Works with all Intex PureSpa models including 28403E, 28407E, 28443E, 28453E, 28421E, 28423E, 28413E, and 28453E 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 24 filter cartridges. This is the authentic replacement cartridge for your Intex PureSpa. It works with all Intex PureSpas models including 28403E, 28407E, 28443E, 28453E, 28421E, 28423E, 28413E, and 28453E. 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.