This water filter cartridge refill pack includes two replacement filters for your Keurig water filter starter kit accessory (sold separately). Simply place a cartridge into the water filter assembly and insert into your water reservoir. For best results, replace your water filter cartridge every 2 months or 60 tank refills. For use exclusively with Keurig single cup reservoir brewing systems purchased after august 2007. This is not compatible with the mini brewing system, mini plus brewing system, the b145 OfficePRO brewing system, or the Rivo system.