I wanted a new battery for my mid 2012 Macbook pro because he was at around 70% of its original capacity but i wasn't sure which battery would suit my Notebook.
Ifixit.com has a step-by-step guide to identify your Macbook pro exactly and without any doubt. The shipping was almost 1/3 of the order but i guess shipping to Europe isn't that cheap.
To sum up, great website, great service and reasonable prices! I recommend it for every person that wants to repair its goods before he/she buys a new replacement.