About a year ago I was rear ended and the shop that did the repairs installed the OEM trailer hitch. When cleaning out the spare tire area I found that the M10x30mm mentioned in the DIY (copied below) were not installed and the parts are nowhere to be found.



Part 7. Install the bumper supports... From the trunk, along the path of the bumper support, you will see 2 weathersealed bolt holes—use a screwdriver or small blade to cut out the black rubberized weatherstripping to expose these holes. Put in a M10x30mm bolt and washer into these 2 holes—hand tighten.

Are they:
Hex bolt with washer 22316761120 Desc: M10X30-ZNS3
Or
Hex bolt with washer 07119903813 Desc: M10X30-U1-10.9
There are several other options as well.
Does anyone know what the ZNS3 and U1 designations mean?
Should I be using an 8.8 grade bolt or a 10.9? I'm leaning toward 10.9 since it has higher strength ratings.
I’m not sure about the thread pitch either.
Anyone have a suggestion?