Popper i think you accidentaly put the same link twice. The difference between the two is: The upgraded one has a clip for the shaft to be stored to, and it has a circuit board to prevent overloading and a cover on the button so you dont accidentaly start it.
The upgraded roto start link:
http://www2.towerhobbies.com/cgi-bin...&I=LXMVE0&P=ML