The RC4wd gears are made of 6061T6 aluminum. I have a full set brand new in my spare tranny.
Here's a couple of pics:
Castle Neu 1520 on 6S LiPo Powered Gmaxx (Nitro Killer)
Predator with OS .21TM
Supermaxx with Mach .26
Revo with OS .18TZ
Kyosho ST-RR Conversion
Ofna CR with Tekin ESC/Motor (2)