HP C9351AE No 21 Black Inkjet Cartridge for use with Deskjet 3920/3940 / PSC 1410. Page yield 150. Genuine HP cartridges ensure reliable and hassle-free operation with your printer. The high quality ink is precision engineered for the best possible speed, quality and reliability when printing, and provides crisp black text that rivals the quality of laser printers. This cartridge is packed with enough ink to print up to 150 pages.