Aftermarket hardened Losi Pinions.   These pinions are made to fit the stock bell giving you more options in size.  The larger the pinion the more top end speed you get but keep in mind, you'll sacrifice some low end torque.   Heat Treated and Made in USA.   
 
** note. you will need new engine spacers to adjust for the difference in size.  You can order the specific engine spacer for your pinion or you may also use the Fonzie universal ones that allow adjustment.
 
https://www.detroitperformancerc.com/product-page/fonzie-adjustable-losi-5ive-engine-spacers