An acquaintance needed a drain plug for his ZF and he's in somewhat of a remote location but his son ordered the part # I suggested from a metropolitan Buffalo NY VW dealer for him. I received the snapshot of what he received tonight. Here's an image of the plug and the part # pick ticket from the VW dealer. A dealer may attempt to substitute this part number but insist on this # and you should receive the 17mm hex. The substitute would be a later "spline" drive instead of the hex. The VW part # is WHT-001-937 that I had posted several weeks/months ago. There is still 17mm hex stock.
There's full size images in my album. Don't know why the "thumbnail" doesn't open larger. Oh well the number is the important information if an OE style fill/drain is needed. Full retail I believe was less than $10.