Easy replacement of the granules of demineralization cartridge 7531</br>For water mist without minerals or limescale</br>3 Packs of Granules per Box - Enough for 3 granules changes</br>Replace granules every 2 - 3 months?? or more frequently in areas with hard water</br>Use: for all BONECO ultrasonic humidifiers except from U7146 Travel</br>Enough for 3 granules changes"to "3 Packs of Granules per Box - Enough for 3 granules changes</br></br>Product Description</br></br>Each box contains 3 packs of granules which is enough for 3 granule changes. When properly installed and maintained?? the BONECO 7533 Demineralization Cartridge Refill Granules will effectively prevent the release of minerals in the air.</br><br/>http://www.amazon.com/gp/product/B001IYMRHGG