I don't know but in all the internet sites i've checked so far the big daddy of the heatsinks is always the swifty mcx462 well something is very strange, the swifty always wins by a small margin of 1 C or even less, i think swifty pays to the websites to show that their heatsinks are better so people will buy them. In my case i don't like swifty because they are bulky and the cooling power just comes from "brute force", anyways is not hard to beat the swifty since other brands such as alpha or thermalrigh just have to make the heatsink bigger so it would cool more. Why the swifty is still the number one? its been awhile like 3 months and i'm tired to read those reviews as the swifty is the best. Thermalright AX-7 or the PAL8045 are in my opinion better than the MCX462.