HP original cartridge. It costs a pretty penny, but because I've not been using 3-rd party cartridges, my laser printer is 10+ years old and still going strong. I highly recommend the HP cartridges, and if you don't use color much, set the properties to monochrome and by the extended capacity cartridge!
The product is good but expensive! The first time a cartridge was shipped the cartridge was used and broken. HP replaced it quickly and the next one worked fine. I have had the printer for a number of years and it still works well!