Brother toner cartridge for use with the Brother HL4000CN printer. The TN-11 Black toner cartridge yields up to 8,500 pages while each of the TN-11 Color toner cartridges yields up to 6,000 pages when printing at 5% coverage on A4/ Letter sized paper. When one of the toner cartridges begins run out, the message "Replace xxxx Toner (x)" appears on the operation panel (xxxx is the toner cartridge color). Replace the toner cartridge(s) as soon as the message prompting you to do so appears. The printer will stop operating if you do not replace the toner cartridge when required. To produce all the colors you see on a page, the individual toners are mixed during the printing process. This mixing of the four-toner colors allows the printer to print in rich vibrant color shades. The Black toner cartridge has a higher yield because black is the Key color for monochrome and color printing.