This set was used during my NHRA Superstock racing days. These MSD modules were measured for resistance from many different sets to find the best possible "linear" curve for starting line RPM and the resulting time delay. It's amazing the variation found with the same labeled module!! MSD's advertised RPM has a certain tolerance around it. I bought many sets to find the best spacing of resistance and therefore the best possible consistency when trying to adjust my reaction time by a perfect theoretical amount. All data will be included with the purchase. The documented RPM range is 4000 - 6000 RPM.  This level of detail allowed me to capture 2nd place in Division 1 in my second year out!!