Product review (4 stars): Great price for an important addition to your health regimen.
The Protec cartridges will filter the impurities in your tap water, leaving your humidifier running smoothly, and keeping its output as clean as possible. The only issue I had is that there was still a little gunk after the winter season while using the Protec cartridges as the manufacturer intended. Nowhere near as much as there would be without the cartridge, but more than I expected. With that said, I still will never go another winter without using these. Incredible product!