Hobbywing XRotor Pro 40A 3D ESC. Brushless speed controller with reversing capability ensures that the spinner bar is just as effective when bot is inverted. Does not require programming or firmware “flashing” like some other ECS’s. Operates with a “soft start” feature. We suggest using with a 3S or 4S LiPo battery. This part is attached to the Spinner Bar Motor of the KINETIC kit.