I have for sale a Dagu Rover track base with 4 dc motors and the Dagu 4 channel dc motor controller with encoder support.This is the same base as Roli but has 4 motors instead of two.Support info available from Dagu or EZ Robot community...Easy to connect to EZB or Arduino..Contact me via my email at [email protected]..$70.00..would do transaction thru Paypal...