POM (Polyoxymethylene)

Also known as acetal resin, POM offers high stability and low friction, like PA. POM is more pliable, making it suitable for long axles that need to be able to flex a little without breaking. LEGO used DuPont's Delrin plastic for at least the watch links, but DuPont isn't listed in their current suppliers list so I assume they use something different now.

Done