If you reset the drum counter during the life of the drum unit currently being used, the remaining drum life will not be displayed accurately. When the Brother Printer drum error machine has printed roughly 15,000 pages, it will display a 'Replace Drum' or 'Drum Stop' notice. To maintain print quality, the drums should be replaced as a set. When replacing drums, unlike toner cartridges, the machine does not automatically recognise the change. Once the new drum is replaced, you will need to reset the drum counter on the Brother HL-L2350DW:- 1. Make sure the machine is on. 2. Close up the front cover. 3. Hold down the “OK” button and the “up” arrow at the same time. 4. Press the “OK” button to select “Drum”. 5. Select the “down” button to reset the Brother Printer drum counter.