This user replaceable maintenance cartridge is an essential component of your printer. It absorbs ink used in print head cleaning cycles, as well as excess ink overspray while your printer is in use. When the maintenance cartridge becomes full and needs to be replaced, you will see a message on the printer’s screen. Replace the maintenance cartridge occasionally to ensure high quality printing and smooth functioning of your printer. For PIXMA G3460, G3420, G2420, G1420, G640