I use 'phenolic' rods (likely one of the various resins mentioned by Pahoo).
There's an appropriately-sized rod in the muzzle-stuffer, and a 48" range/cleaning rod.
I do not recall the brand. If I had to guess, I might go with Delrin as the material. Though, they could be acetal, as well. They're quite flexible. So if that's not a characteristic you'd like to deal with, then stay away.
One of my brothers once tied an identical 48" range rod in a knot, just to see how far he could go before it broke. It didn't...
But, they're still stiff enough and strong for normal loading, cleaning, ball-pulling, etc.