I own a Macbook 5,1 (unibody), last week I bought 4gb memory frow OWC. Yesterday, I tried to install it and the 204 pin kit got jammed. Since, I didn't want to damage the RAM or worse the Macbook itself, I brought it to an Apple Store for repair. Today, while reading the Mac's instruction booklet, it says that I should be using 200 pin PC3-8500 DDR3 1066MHz SDRAM while everywhere on the internet, it says that this computer uses 204 pin PC3-8500 DDR3 1066MHz SDRAM. Now I wish I haven't caused any permanent damage to my MB by forcing 204 pins into 200 pin slot!