We developed core series for mini sumo robots specially. 

We recommend for all robot makers for their good price and high power output. What is more that you can overvoltage motors up to 18.5 Volts (5 cell Lipo). It's bigger motor diameter gives enough time for cooling.

Core series are very popular so grab them if they have stocks at our website. (Usually fast sold)

http://www.jsumo.com/core...