These printers use the C8061X cartridge:

HP LaserJet 4100

HP LaserJet 4100 D TN

HP LaserJet 4100 MFP

HP LaserJet 4100 N

HP LaserJet 4100 Series

HP LaserJet 4100 TN

HP LaserJet 4101 MFP

TROY-Systems Troy 4100

TROY-Systems Troy 4100 EX