The Idea of the liquid Pro and Ultra is that they loose the Moisture in them and then becomes a solid metal contact between the two surfaces, and because it is so fluid if you try to mount a cooler on with both surfaces being smooth and have too much on there it will all just push out the sides, then you have little balls of conductive metal all over your motherboard, as in the pictures on the article, this is not something you want. Also it affixes a lot more tightly so it is hard to remove the heat sink, requiring twisting motion to loosen, probably not a good motion to use on mounted RAM sticks.