Ink cartridges and drum units are the consumables used by printers, faxes or franking machines that are used to apply the ink or toner powder the machines use to paper or other media. Laser drum units contain a photoconductor drum (like a glass roller) under a flap. Ink jet cartridges are equipped with an electronic chip (rather like a SIM card). These shouldn’t be confused with ink tanks or toner cartridges (also known as refill cartridges or waste toner boxes).