Yeahhhh, the short solid chunk is 12mm... So... I threw it in the mill and took 1mm/side off of all 6 sides for the first 3/8" or so, and voila, I have an oil plug wrench now...
There are two drain plugs, are they both 10mm? Which one are you referring to? The tool I am missing is the one closer to side of the bike that has the fill port and where most of the oil comes out. On mine it is an allen type bolt that I ended up using a 3/8" allen wrench on. On pages 38&39 of the parts manual it is described as: Plug (M 22x1,5). I just want to get the right tool for this since the one in the kit does not fit it.
The big plug takes a 10mm Allen, the small plug is 12mm wrench/socket. Careful using a 3/8", you may eventually round off the wrench or worse, round out the socket in the oil plug.
And what a stupid piece they put in the tool kit. It keeps disappearing inside the axle! I'm going to drill a hole and put a little set screw in it so it stops before gophering on me. Probably easier to just carry a 12mm allen wrench...