Two iPhones 3GS 32GB with low battery performance.
The replacement is easy and the last flat cable to install back is the only that requires more attention is is a little difficult to reinstall it. The battery shipped and tools are great.
I had a problem before with an iPhone service store where they couldn't replace the battery from these iPhones. Their argument was these phones are from Brazil. It's not true, there is no difference between the iPhones worldwide.