This is the Standard Crankshaft Version of the Traxxas Pro TRX-15 Engine.
It is for those who want higher performance than a .12 size engine in...

     

This is the Traxxas 2.5R Racing Engine with IPS
(Integrated Pilot Shaft) and Pull-Start.
For use in all Traxxas vehicles that use the TRX...

     

This is the Traxxas TRX 3.3 Racing Engine with Pull Starter.