still to date i havent found out if the are steel or ceramic!!
yeah they are ball bearing, i am running 14psi thro mine, keeping it safe as i was told the did have steel wheels on, from a scratch test but i stiull wanna be safe. my car is making 321rwhp or 239.8rwkw's with 14psi. and a slipping clutch haha!
good luck and i hope this helps