We all know that black ink is the most used of the cartridges in your printer and that is why Canon provide this BCI-3e Black ink twin pack. Buying the two cartridges together makes both cheaper than paying separately for both. It also means that, should your black ink run out, you have a spare ready to go. Together these cartridges can print up to 3,000 A4 documents though this number is a lab test total which makes them the absolute maximum. If you have an older printer or your printheads are dirty you can expect to print a little less.