These printers use the KX-P450 cartridge:
Click On a Printer to View it's Cartridges
          Panasonic Fax KX-4450
          Panasonic Fax KX-4451
          Panasonic Fax KX-4455
          Panasonic KX-P 4450
          Panasonic KX-P 4450 I
          Panasonic KX-P 4451
          Panasonic KX-P 4455
          Panasonic UF 725
          Panasonic UF 750
          Panasonic UF 750 D