they have detrimental affects, even the non conductive ones, but only by 1-2C. I actually get better contact on my celey as the POS Retail was sitting at an angle and the shim leveled it out. I wouldn't make them though, they have to be made very precisely and if you make one too short, its pointless, too high, you never make contact with the core which is very bad. If you want one, several places sell the nonconductive ones. I wholly recommend one for a GW hsf as I cracked the core of a duron with one and I will take the worst results to save another $30. But if you have a hsf with a much better mounting system(Swiftech's is the best) such as a Vantec, you don't need one.