The battery replacement to end all battery replacements
My friends MacBook pro Mid 2011 was heavily used and the battery indicator actually suggested that it be replaced soon. So I ordered the kit to replace it.
Super simple and the battery fit without interfering with the touch pad. I tried a cheaper alternative from another online retailer that shall not be mentioned, begins with an "A", this cheap alternative while works, added pressure behind the touch pad, enough so that the clicking mechanism no longer worked. I sent it back and went for the iFixit kit at greater expense. Worth every penny, installation was a cinch, and the battery did not interfere with the touch pad by design. I will never order a 3rd rate battery again.
Do not even consider going anywhere else for your battery replacement needs when it comes to the older MacBook pros. The cheaper versions just are not designed to the exacting standards of Apple products. iFixit should be your first and last point of service for all your computer or iPhone or iPod related fixes. I have also replaced a bad battery for my daughters iPod from iFixit, and it is still going strong.