I am a machinist not a writer I have trouble explaining things in righting so i will try again . the adapter nut is threaded on bothe ends 10 mm by 1.0 and 10- 32. thare are to steps from the 10 mm side one is 12 mm and the other is the same as the washer i think it is .5 the 12 mm is the same as the cank shaft so as you tighten the nut it will move into the washer and the prop. the pic you have is the stock nut not the spinner adapter nut. the prop hole is 12mm the theads are 10 mm so thare is clerance for the nut wich has a 12mm OD step to a .5 OD step. I hope you can under stand this I wish i had AUTOCAD thin i could show you the adapter nut i made or camera.