Are these round black 1x1 pieces LEGO? A friend encountered two pieces of plastic in a bulk lot of LEGO she bought and was wandering if they were actually LEGO, a clone/custom brand or something else entirely...
She sent the following pictures:







There are no markings or numbers on the pieces.
They do seem to fit on LEGO studs:

I don't recognize the pieces so I assume they aren't LEGO.
But perhaps someone here can identify them?
These are Lego parts.

The part on the left is a hose end (752). It is found on the ends of hoses like this:



The one on the right is 6221 (Peeron 424).



This part was most commonly found in older Technic sets as a spacer or crank handle: