Best is to use one single kit. Second best is to use two identical RAM modules. In theory you could use any two or more sticks of RAM but until you try there's no guarantees it would work. It's just try and see what happens proposition, might or might not work !!Can I use Corsair and hyperx fury 8gb ram with same MHz in my system? or I have to use the same stick in my pc to get 16gb? plz help