Oil pan plug size on 2006 Buick Lucerne

I am trying to determine the exact size of wrench that will fit the oil pan plug on my car. One 14mm socket fits it, but a 14mm open/closed end straight wrench is too large. What is correct?

2 answers 1 comment
Some show 13mm and some show 14mm use the boxed end as long as its snug it will be fine.
Using a wrench a 13mm will fit it.
13mm seems to fit pretty snugly. No room for a drive though, just use a box wrench.