A few weeks ago, my mid-2012 MacBook Pro suddenly shut down and started to beep out the code for a RAM error. Trying to turn it back on never lasted more than a few minutes before it shut down again, and none of the solutions suggested online related to reseating the RAM sticks worked.
This product did the trick! After a 5-minute install, my Mac was back to great working order.
A tip for anyone in a similar situation: A MacBook Pro can run fine on one stick of RAM. Try using each stick individually to see if one still works, and that will help you keep working while you wait for the replacement RAM to arrive.