Hi By a strange coincidence I loosened my 1995 Boxer(Petrol) Drain plug yesterday,in order to reduce the amount of oil in the Engine. I tried my Ring spanners, and found out that it was a 21mm spanner, which I didn't have, so tried my Plug Box spanner and it fitted perfectly. My Drain plug was a bit too loose for my liking, but yours has obviously been tightened by the usual Garage Gorilla!! Andy :roll: