I just installed the RAM sticks on my macbook bought in 2011. It took 10 minutes and saw my macbook! Since the transition to Yosemite (I should have avoided) he rowed with his lot 2GB RAM. I hesitated between 4GB and 8GB and I have done well to 8GB memory clean because the implementation tells me that I often use 4GB. My macbook is fast again. In stock were asked 50 euros workmanship. I'm glad I made even me (there are cars on youtube) Please, give it back a few years of extra life to your MacBook for 90 euros! it's a gift!