These printers use the 621-1 cartridge:
Click On a Printer to View it's Cartridges
          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