These sticks have been sitting in storage, and when I last used them, they were in working conditon. But I cannot guarantee that now, so it is up to you if you are ok with the risk.The total amount of ram is 20gbs ddr3. Three of the sticks are G.Skill Ripjaw DDR3 at 1333 mhz, and the HyperX is 8gb DDR3 at 1886 Mhz. I believe you will be able to put mix them, but I cannot guarantee the out of box stability, you might have to play with the bios to get it right, or it could work instantly without any need to mess with things. If you have any questions, I will try my best to help. Thanks!