As the name implies, the Professional Racing Ignitions are made for professional, extended, high-RPM racing. These feature NASCAR-required harnesses, a clear base plate and vibration-dampening silicone. These use a special coil (PN 8250) and produce more voltage and spark energy.
For heavy-duty applications like off-road truck racing or dirt racing tracks, the 6ALN is a great choice. Epoxy for vibration resistance and sealed locking connectors combine to make an ignition that can handle the demands of hardcore racing.