Note: These cartridges have "smart-chips" which enable the printer to recognize when the cartridge has emptied. We provide refill instructions, but you will not be able to monitor your toner level electronically; you will have to watch the quality of the print to evaluate when to replace toners. This is not a problem for most people, and is offset by the huge cost savings of buying the refill kit. If you would prefer the ink-level feature re-enabled, you will need to replace the smartchip. The smartchip is optional and available for the HP 1500 and HP 2500 (see smartchip for HP 1500 / 2500). There is no smartchip replacement yet for the HP 2550.