'Cause they're metal, not plastic. And because one of them has a key way stylee slot rather than a hole and because I'm anal and want it right and because I can't be arsed/don't have time to be fecking about filing a slot in a standard washer myself, if I can just get a proper one and slip it on and by the way yes I did type all that on a single breath without breathing and I can still carry on doing some more on the same breath as well so ner no punctuation needed here matey no way no no no no no...