Yeah, those are a direct replacement for the stock steering knuckles. They're off the Mad Bison or some other such TL01 based off roader not quite sure. Made from graphite reinforced plastic like the stuff used for the reinforced Mini wheels. A lot of guys ran these during TCS a couple of years ago as they are a lot stronger than the stock items (but will still snap in a suitably horrific smash) they were popular because the Tamiya alloy knuckles are expensive (but worth the investment) Eagle Racing also make alloy knuckles which we have on one of our Minis, they are a lot cheaper but not TCS legal.