These printers use the CE505X cartridge:
Click On a Printer to View it's Cartridges
HP LaserJet P-2050
HP LaserJet P-2050 DN
HP LaserJet P-2050 X
HP LaserJet P-2055
HP LaserJet P-2055 D
HP LaserJet P-2055 DN
HP LaserJet P-2055 X