is perfectly flat.... I dont see them lapping it to the CPU's crown.. Lapping is the mating of surfaces.. dictionary.com demonstrates this term: Lapping: To hone (two mating parts) against each other until closely fitted.. The best way to do this would be to use lapping compound between the sink and the crown and some sort of tool to gyrate one of the parts. some places lap the cpu as well but in most cases you just can't do that with a processor with exposed core... anyway it just shows that it can be done right on your own w/o a third party and for a HELL of a lot cheaper. and that gives ppl an idea of how to polish to a mirror finish that is the only reason it was posted.