The underside of the heat sink is pure copper as is all of this product, it looks like a little bit of lapping was done to the metal during manufacture so you don't need to bother. The clip mechanism is adequate for a heat sink of this weight (476 grams) and once on wont be going anywhere . Thermaltake uses a clip that covers all 3 lugs on both sides of your CPU socket, this isn't a tooless design but using the right sized screwdriver in the slot it went on with no problems at all.