Ahhh I figured it out.
I'll post this info so that someone else doesn't run into the same issue.

I ordered part Rein BKN0100R from Rockauto because it matches the OEM part number 31607565315

It arrived and the diameter is so big.

Looks like the Rockauto system is not properly organized.

I looked again, and I see another part, Rein BKN0061R which is also listed as inner boot.

I suspect BKN0061R and BKN0100R are two different boots with different diameters.
Since BKN0100R did not work, I suspect I need BKN0061R.

However as per screenshot, the OEM numbers listed for both parts are the same, which it cannot be.

Furthermore, Rockauto does not list the diameters for the boots, so it's impossible to figure out which is correct...
I wanted to call Rockauto but they got rid of their customer service on the phone and everything is fully online now.

I attached a second image of what I believe are the correct dimensions for the inner cv axle boot