One of the most notorious issues with Intel's Prescott Pentium 4 is its tremendous heat dissipation. Dealing properly with the heat produced by this CPU requires care on the part of the user in selecting the appropriate cooler. To help make that a little easier for you, THG's Munich Lab has tested 5 Pentium 4 coolers for socket LGA775.
One thing is immediately obvious when you consider the coolers: they all look somewhat similar. All the manufacturers have obviously been inspired by Intel's reference design. The basic shape of each of the coolers is the same, with only the EKL cooler differing slightly: its aluminum heatsink is oval instead of round.
Why do you suppose that is that the case? The reason is that Intel's thermal design guide specifies that airflow from the cooler also must cool the surrounding motherboard components, especially the voltage regulator. It is not easy to implement this type of cooling design, so manufacturers have generally stuck to Intel's reference design.
Extract from Intel's thermal design guide.
Intel's RCBFH engineering sample.