It doesn't matter. Get at least 8gb and get 1.5 volt ram of decent quality. Those are the 2 most important things, the rest does not make a difference you will notice.
It has excellent latency and a good clock speed. IMO, anything faster than this is money down the drain.
That is good ram. I don't wanna flame war or anything, but intel recommends 1.5v and not over 1.6 for ivy bridge memory controller. 1.5 plays it safe for whatever he gets and means it'll boot.