Question about heat ranges in Champion plugs

Here's my question. If you look at the picture that I took you will notice that the one on the right is a colded than the left.
The heat number on both number 12. You can see in the photo that the numbers are the same except for the hex head.
I would really like to know.
Thanks................Ted

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A 12 is always a 12. Doesn’t matter what shell is on the plug.