Product review (5 stars): Air-O-Swiss AOS 7531 Demineralization Cartridge
We buy this item on Amazon.com because we live in a remote area of Montana and shopping is 60 miles one-way away (besides, the prices are up to 40% higher and with Amazon delivering FREE to our door within 48 hours, why go anywhere else?)
Anyway, these are the same name brand I have bought elsewhere for a lot more and they are excellent.
We have used the Air-O-Swiss for many years and these filters are original equipment and keep the humidifier clean and clear.