Champion Spark Plugs, a wholly owned brand of Federal-Mogul Corporation that specialises in making spark plugs for automobiles, has the RJ19LM and the J19LM in its product line-up. Although they are essentially the same, the "R" designation of the former indicates an added feature over the latter.
The RJ19LM has a resistor, which is placed in the spark plug's copper core. It functions as a suppressor of radio frequency interference, or RFI. This refers to the static you get from your car radio, or interference from other sensitive electronic components in your car. The J19LM, on the other hand, lacks the resistor, thus making it much more susceptible to RFI.
Champion makes each RJ19LM and J19LM with a corrosion-resistant zinc-plated shell. Its measurements include a 14-millimeter thread, a 9.5-millimetre reach and a 20.6-millimetre hex.
As of December 2010, Champion Spark Plugs suggests a retail price of £1.80 for the RJ19LM and the J19LM. Customers can purchase the spark directly from the manufacturer by going to its website.