These printers use the 621-1 cartridge:
PitneyBowes-Imagistics DM 500
PitneyBowes-Imagistics DM 500 POSTAGE METER
PitneyBowes-Imagistics DM 525 MailING System
PitneyBowes-Imagistics DM 550
PitneyBowes-Imagistics DM 550 POSTAGE METER
PitneyBowes-Imagistics DM 575 MailING System
PitneyBowes DM 500
PitneyBowes DM 525 MailING System
PitneyBowes DM 550
PitneyBowes DM 575 MailING System