17mm.........you can get a 17mm allen wrench at sears Al Streicher wrote: > Can someone tell me the correct size for the hex bit, that fits the > Diff. Filler Plug? 15-17-19mm? > Can I use an "allen wrench" or is the hex bit socketbetter? Who sells > it? > Thanks > > Al Streicher > Rathdrum, Idaho > > '90 80 Black