I can't seem to find the answer to my question any where. I was needing to know if the hd in the WD 500gb My Passport essential is 9.5mm or if it is too large to go into a 2.16ghz black macbook. According to the western digital website the casing measurements of both the 500gb and the 320gb are the same, but I cannot find anywhere the exact model number of the hd within the casing. Any help would be great, thanks.