On Thu, 7 Sep 2017 14:54:58 -0000 (UTC), Mad Roger
wrote:

Why so many spark plug numbers for the same thing?

Here's a photo of the tag on my Echo leaf blower.
http://www.bild.me/bild.php?file=9232473sparkplug.jpg

Of course they don't have that size at Home Depot, but they have a
Champion 852ECO

Looking it up, it seems that they all cross reference to
RCJ6Y, CJ6Y, 5852, 852EZ, CJ8, J6C,QCJ6Y, BPMR8Y, BPM8Y, & E3.12

Why so many spark plug numbers for the exact same thing?

Half of those refer to whether it is a resistor or non resistor plug.
I doubt you have an AM radio in your leaf blower and you would not be
able to hear it if you did so it really does not matter which of the
two you use.