Canon MP-560 - cartridge question

I'm thinking about buying a Canon MP-560 printer. I find two types of cartridges listed for this printer: CLI-521 and CLI-221. Are these identical cartridges? It looks like the 221 is a US version and the 521 is a european version? I want to replace the original cartridges with refillable ones and can only find replacements for the 221 type. Will these fit a printer that comes with the 521 type cartridge? Thanks for your advice.