Extra hard high carbon motor pinions are built to last with our hi-performance GEN3 steel slipper units. Made from high carbon steel and then heat treated to increase the hardness of the surface even further. High carbon steel is naturally lower in friction and adhesion than milder grades of steel making these gears ideal for use with metal spur gears. All pinions precision machined and stamped with the number of teeth. One 4 m/M set Screw included. 2 m/M Allen wrench (not included) Fits the 4 m/M set Screw. Can be run on motors using a 5 M/M motor shaft including Traxxas, associated, and Hei models or for any heavy duty application. Tech note: rrp#1200 5 m/M to 1/8 inch reducer sleeve required for 1/8 inch shaft motors.