You don't have to, my boss put his on without lapping it, and had no trouble, but as there were still pretty noticable machining marks, and I had jsut spent $22 or whatever for an aftermarket cooler, I wanted to lap it so I got best contact, and hence best performance from it. THe heatsink is raised from rest of card probably at least a quarter inch though, so should be able to get ramsinks on there no problem. Make sure of whether or not it's compatible with your card though, can't remember if it works with the 9500. T hink it does, but will save some hassle of you make sure before you buy it.