These printers use the C1806A cartridge:
HP DesignJet 2000 CP
HP DesignJet 2000 CP-UV (for Dye Based ONLY)
HP DesignJet 2500 CP
HP DesignJet 2800 CP
HP DesignJet 2800 CP Wide Format Color
HP DesignJet 3000 CP
HP DesignJet 3500 CP
HP DesignJet 3800 CP
HP DesignJet 3800 CP Wide Format Color
HP DesignJet CP CAD
HP DesignJet CP GA