I have brought these around at the lowest price I can so as to give the people running MSD and burning plugs the option of the "best" plug on the market. Really they or any other plug will not outperform a equal plug from another company but they are much more durable and available in many stages depending on the temp range needed. Mostly Nitrous cars that are track based use them. There is a big nitrous following in LA and most of them go with Denso. If NGK, Delco, or even chunk of steel is working then there is no need to change. If you buy a NX or other Nitrous system from DP we will push the Denso because they are much better for the NOS application. If you donít mind changing plugs it fine to use copper plugs with the MSD systems.