Lexmark C540X31G Black Developer Unit for C54X Printer For use in Lexmark C540DW, C540n, C543dn, C544dn, C544dtn, C544DW, C544n Works in 546Dtn, X543DN, X544DN, x544dtn, X544DW, X544N Also compatible with x546dtn, x548de, x548dte