This Water Filter Cartridge Refill pack includes six 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.