In praise of hard fiber washers

I got a pack of a hundred 3/8" ID 1" OD hard fiber washers from Amazon's Industrial and Scientific sale on sale for under a dollar as an experiment (the regular price is about $16).  A significant portion of my do it yourself budget seems to be washers, so I thought it was worth trying these.  They're great.  The ones I got are black and not glossy so they're suitable for use inside a telescope without painting.  They are a bit thicker than steel washers and a bit thinner than nylon.  They are super-hard, lighter than steel and of course don't corrode.  I know this post sounds like an ad, and to alleviate that impression, I'm not linking.  But search for "fiber washer" in the Industrial and Scientific store, and sort by price from low to high.