These MSD 6AL #6420 ignitions are the perfect choice for the street or the track. The powerful capacitive discharge, multiple sparks ensure complete combustion of the air/fuel mixture to increase power and performance. MSD has taken the proven performance of the 6A and added a rev limiter. The soft touch rev control will protect your engine from overrevving. Adjustments are easily made with plug-in modules, so there are no dials, switches, or programs to deal with. At your selected rpm, the soft touch begins dropping the spark to some of the cylinders, and on the next cycle, these same cylinders are fired to prevent loading up with fuel. The result is a smooth and accurate limiting action without backfires or roughness. They’ll work with virtually any 4, 6, or 8-cylinder vehicle with a distributor, as long as it has a 12-18 V electrical system. They include rubber shock mounts and modules for 3,000, 6,000, 7,000, and 8,000 rpm. CARB D40-26 approved in all States.