These printers use the 6R343 cartridge:
Click On a Printer to View it's Cartridges
Xerox-Tektronix 6 G4
Xerox-Tektronix 5008
Xerox-Tektronix 5008 RE
Xerox-Tektronix 5008 S
Xerox-Tektronix 5240
Xerox-Tektronix 5260
Xerox-Tektronix 5280