The HP 21 Black Inkjet Print Cartridge combines patented ink formulations with advanced inkjet print cartridge technology to ensure crisp, laser-quality black text every time you print. Pigmented black inks provide crisp sharp text for your letters and reports-documents you can be proud of from your HP printer. Keep your documents for a long-term reference. Printed text from this HP ink remains dark and sharp longer. Results you can count on across a broad range of plain papers and specialty media. Print greeting cards, homework assignments, letters, e-mail, and reports with confidence.