22 parts.

• 25D mm Motor with 48 CPR Encoder (no gearbox)Pololu
• Aluminum Scooter Wheel AdapterPololu
• Breakout for JST SH-Style Connector, 6-Pin MalePololu
• Current Sensor CarrierPololu
• DC Motor DriverVarious
• Distance SensorVarious
• IMU BoardVarious
• Maestro USB Servo ControllerPololu
• Magnetic Encoder DiscPololu
• Metal GearmotorPololu
• Micro Metal GearmotorPololu
• Motor BoardsPololu
• Motor BracketPololu
• Plastic GearmotorVarious
• Pololu WheelPololu
• QTR Reflectance SensorPololu
• Reverse Voltage ProtectorPololu
• Scooter Wheel Adapter PlatePololu
• Stepper MotorVarious
• Tic Stepper Motor ControllerPololu
• Universal Mounting HubPololu
• Voltage RegulatorPololu