HP 902XL magenta · XL

The HP 902XL magenta is one of four separate tanks used by the OfficeJet 6958, OfficeJet 6962, OfficeJet Pro 6968, OfficeJet Pro 6970 and OfficeJet Pro 6978. Separate tanks are the good news on this design, because a heavy magenta job does not force you to bin usable cyan and yellow the way a tri-color cartridge would.

There is a catch that surprises people. The print head sits in the printer and draws a little ink from every tank during its servicing routines, so these machines will not carry on printing with one tank empty. An exhausted magenta stops the black text job as surely as it stops a photograph, and there is no driver setting that talks the printer out of it. That makes a spare of whichever colour you use most worth having in a drawer rather than on order.

On price it is rated at 825 pages for $30.00, which is 3.64 cents a page. The black in the same family is 4.61 cents, so the colour tanks are the cheaper pages here. A full set of four cartridges lists at $128.00.

Every printer that takes this tank is on our firmware lockout list because of HP Dynamic Security. A firmware update can start rejecting non-HP chips, so if you plan to run compatibles, stop the printer checking for updates first and keep the receipt until you have watched the cartridge print a page.

Low magenta shows itself before the printer says anything. Reds go orange and skin tones drift yellow while the rest of the page still looks normal. Check that against a nozzle check before buying, because a partly blocked magenta nozzle produces the same shift on a tank that is still half full.