Needed for our Radio Controlled Trucks if not buying our multi-function unit: 56348 or 56511 . The TEU-105BK is a forward and reverse running electronic speed controller featuring a high frequency wave drive system. The TEU-105BK is intended to operate the included 540 motor (27 Turns) found in most of Tamiya's assembly kits. The 105BK can handle up to a 25 Turn Tamiya Torque Tuned motor. The TEU-105BK is compatible with Lithium-Ion battery technologies, and includes a battery cut-off function to prevent over-discharging of the main battery pack. Alarm and LED warnings indicate no-signal status. Caution: Motors rated below 25 Turns are not meant to be used with the TEU-105BK and should not be used.