In addition to the toner cartridges for your C-EXV21, you also require a Canon IRC-3880i and the additional three imaging drum units for the successful running of your printer. The original Canon 0456B002AA imaging drum unit is instrumental in the handling of the black toner powder from its corresponding cartridge and you simply cannot run your printer without it.
Thankfully this genuine Canon 0456B002AA imaging drum unit has an amazing estimated page yield of 77,000 prints, so they seldom need to be changed and the cost per page is mercifully low too!
