Hear me out, I understand you would want the same RAM with the same ghtz and manufacture preferably. But my friend is getting a new PC and he asked if I wanted his old RAM. I currently only have 2, 4 GBs of HyperX DDR3 RAM 1600 my only problem is, I dont exactly know if he gives me is DD3 RAM is that going to cause problems? They are also 2 sticks of 4 GB RAM but its "G.SKILL Ripjaws X Series 8GB (2 x 4GB) " is it ok to put that in my PC with my current RAM? Or should I just say no and then go buy 2 8GB sticks to get 16 GBs of RAM with my Amazon Giftcard.