What is the Difference Between PGBK and PGI Ink?

Looking for a PGBK cartridge but can only find PGI? This is a common issue which arises from the way Canon label their printer cartridges. The “PGBK” part of the cartridge name is a reference to the the ink inside and is in fact an additional designation to PGI. This isn’t particularly clear because the only place you’ll see PGBK is on the cartridge packaging (which Just Ink and Paper often removes to make sure the package will make it through your letterbox) or on the body of the cartridge itself. Many of the product packaging images are a little too small to see the PGBK label and you can't see the cartridge until it's delivered but rest assured a PGBK is PGI by another name.