The surface gap plugs do not have any extended tip at all, so they are ultimate "cold" plug. I guess one could say they have no heat range at all. Since they do not burn off the deposits, they rely on the very fast high voltage spark to fire them at all. The conventional gap L77JC4 has a very short tip, so they are still a very "cold" plug, while being more tolerant of spark conditions. In later years the L77JC4 was modified to QL77JC4, the Q meaning it has an inductive RF suppressor so it does not cause noise and static on your electronics.