Replacement chip for HP 4600. The HP 4600 cartridges are designed with a chip so that the printer can remember how much toner is left in the cartridge, and therefore warn you when you are running low on toner. This feature of the HP 4600 printer / cartridge is called "diagnostics". Without the chip, the cartridge will not print. We offer 2 reset procedures (manual reset procedures), so that you can "overide" your old HP 4600 chips, and thereby allow your printer to continue printing. These reset procedures work for over 90% of customers and allow the customer to continue printing, but do not allow the diagnostic feature to function (this means you can print, but you will have to watch the toner quality to determine when you are running low on toner). To re-enable the diagnostics feature on the HP 4600, and for a 100% successful refill / reset, you will need to order these cartridge specific HP 4600 replacement chips. Its quick and easy to replace the HP 4600 chips and restore your cartridge to "new" specs.