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