HP holds a 17 year patent on their cartridges. Our factory will refill the HP51626A, HP51629A, HP51645A and the HP51641A if you wish not to refill yourself. I have a Cannon printer and an Epson printer. All inks are different. Printer manufacturers design inks for the specific cartridge, with changes in viscosity, ink delivery systems, pH levels and surface tension.
Some inks are pigmented, some are water based.
You can ruin your cartridge and clog your print heads by using the wrong ink to refill your cartridge. It is against the law to void a warranty for use of a compatible product. No printer manufacturer can mandate that you purchase only their replacement products. Compatible inkjet cartridges are high quality, cost effective alternatives to spending a fortune on OEM cartridges. I don't like to use my credit card on the Internet.