Yep on the 14MM. When I did my tank, I didn't have a way to get the 14MM hex socket, so I used a 14MM grade 5 or grade 8 bolt with the end ground square so I could put a lock wrench on it.
The 2nd time around I got the 14MM hex socket
The nut on my bike was on with red loctite. It was NOT fun to get off.