Heavy duty steel material, fit X-0483 Z-S0058 Black Yota or Silver version Z-S0019 as fitted to the Trail Finder 2 Kit Z-K0042.

You may also want to considering upgrading to XVD for improved reliability and increased steering Z-S0342. If your bearings are worm replacements are HERE  and Bevel Dif Ring and Pinion gears in stock form are Z-S0027 and Helical for improved performance are Z-G0059.