The Noritz SS-HBC-2 has been discontinued from the Noritz line
Order Replacement Cartridge
However, if you already own an HBC-2 and would like to still order replacement cartridges you can still do so from our partner manufacturer. Please be ready to give them the Noritz HBC-2 model number and they can assist you.
The compatible cartridge will be the SS-EXT
HydroBlend ScaleStick – Southern filtration & Equipment Systems (sfes.com)