snake oil, expensive snake oil, i question how long they actually last and when the cap fails it probably just reverts back to a regular spark plug, the kv of the spark is dictated by the conditions in the cylinder, the coil may be capable of 40kv but the plug is usually only drawing like 8-12 at idle, i've not measured one at full load (sure it would go up as cylinder pressures rise) no load revving it goes down
all america wants is cold beer warm cat and a place to take a poop with a door on it