Open the ink access door on the front of your HP OfficeJet Pro and look at the cartridges already installed — each one carries its ink number on the cartridge body, for example "HP 938" or "HP 938e". Most OfficeJet Pro models also list the installed cartridge numbers on the control-panel display under the Supplies or Ink Information menu. Match that number to the cartridge you are about to order. If you are still unsure, send us your printer model and we will confirm it for you.

Both HP 938 and HP 938e EvoMore fit the same machines: the HP OfficeJet Pro 9100 series (9110b, 9117b, 9120, 9120b, 9122, 9123, 9125, 9128, 9130, 9130b, 9132, 9133, 9135 and 9135e) and the wide-format HP OfficeJet Pro 9700 series (9720, 9720e, 9724, 9730, 9732 and 9734). The full list is in the Compatible Printers tab above.

HP states yields as an approximate average based on ISO/IEC 24711 or HP’s own testing methodology with continuous printing, tested in the HP OfficeJet Pro 9100 series. It is a standardised figure for comparing cartridges like for like, not a guarantee — your real-world yield varies considerably with page content, how much of each colour you use and how often you print. The per-colour figures for this family are in the Page Yield (ISO) tab above.

Yes. AtomOffice supplies Original HP ink only, sourced through official HP channels — never compatible, refilled or remanufactured stock. Genuine cartridges matter particularly on these machines: HP OfficeJet Pro printers are dynamic security enabled and are intended to work only with cartridges carrying a new or reused HP chip.

If you print in volume, the high-capacity HP 938e EvoMore range is usually the better buy — it is rated at roughly double the pages of HP 938 (about 2,500 pages in Black and 1,650 pages per colour), so you change cartridges less often and the cost per page is lower. For light or occasional printing, standard-capacity HP 938 keeps the up-front cost down.

Yes. HP lists HP 938 and HP 938e EvoMore for exactly the same OfficeJet Pro 9100 and 9700 series printers, so you can switch between them at any time — and mix them, for example a high-capacity Black alongside standard-capacity colours.