Ink Refill Kit for HP Officejet Pro 8500 Printers using HP 940 Cartridges Highly Reliable Clog Free Formula - Archival ink is filtered to 0.2 um, which is the same as original ink. The advanced archival ink formula prevents ink foam from appearing in the ink chamber Precisely Calibrated Ultra Wide Color Gamut Equivalent to 40 Cartridges - Save $600 Compared to Buying New Cartridges Simple and Convenient Refilling Process