Because after upgrading to Snow Leopard Mountain Lion and then Maverick my MacBook Pro always been slower, especially when several applications open, I have to upgrade to 2GB of RAM installed ursprüngich performed to 8GB with the purchased modules here. The exchange was no problem after removing the bottom cover (screwdriver PH00 required): Old modules out - new modules purely - done! A short test after starting the Mac was in "About This Mac" 8 GB of memory on - the modules are correctly recognized! In detail is actually recognized as manufacturer Samsung. So I was able to put the cap back and enjoy since the "new speed" of my MacBook Pro.