The ink of your HP OfficeJet Pro ran out. Depending on your printer, you need new HP 937 cartridges. The 937 HP cartridges are suitable for the HP OfficeJet Pro 9120 and the HP OfficeJet Pro 9720, for example. You can read for which other printers the HP cartridges are suitable on the product page. There are separate cartridges and combo packs. You can print up to 800 pages in color. Want to print more? An XL cartridge is a better choice.