Roughly there are all clocked 1333MHz 2x 4GB ties with 204Pins of Samsung.
Are you normal user and want to easily upgrade your system, the following lines ignored. Buys the Ram, he will run and you provide good services (Samsung flat).
(But Are you interested in art and play in the bios on the voltage of the Ram rum, then read quietly.)
More specifically, they single out small, but subtle differences.
Thus, there are the:
M471B5273DH0 run at 1.5V and 1.35V
M471B5273CH0 run at 1.5V and 1.35V
M471B5273BH1 only run with 1.5V
For the other differences you can stop by on the Samsung website.
[...]
Now to the actual product:
For me he has been running since March in a 2011 Macbook Pro with no problems.