Every metal surface on every heatsink that I have ever seen has a lot of little imperfections in them. It simply isn't possible for the manufacturers to produce perfectly flat bottomed heatsinks. They are good enough for you to use but by doing something called lapping you can usually lower your temps a few degrees. Any real mod freak will want to lap the heatsink on your northbridge as well as the one on your CPU. Today we will be lapping our Northbridge heatsink but you can use the same principles on your CPU and heatsink.