“Metal shards inside the shower head of the place I’m renting? What are these and why are they in there?”
Answer: "Surely they are solder from copper plumbing. If you overheat the pipes while soldering, long strands like this can form on the inside. Definitely a sign of improper soldering, if that’s what they are."
I have one that has been in use for over 80 years, there is nothing missing on it.
Driveway marker