These printers use the KX-P450 cartridge:

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