Nature2® W22465 Swimpure Single Cartridge For Cartridge Filter, 3'', 35K gals, 6/Pack is used on the N2CN35 (35K) filters. It will also work on the Nature2® Cartridge Filter Drop-in Mineral Dispenser. The patented Nature2® mineral technology by Zodiac Pool Systems uses safe, elemental mineral ingredients to create pool water that is noticeably cleaner, clearer, and softer. Minerals such as silver and copper have long been known for their sanitizing antimicrobial properties. With Nature2® cartridges, Zodiac brings that natural sanitization to your swimming pool.