RioRand (TM) 12V-40V 10A PWM DC Motor Speed Controller w/ Knob--High Efficiency, High Torque, Low Heat Generating with Reverse Polarity Protection, High Current ProtectionFrom left to right they are Motor-, Motor+, Power-, Power+Features:Control the speed of a DC motor with this controllerHigh efficiency, high torque, low heat generatingWith reverse polarity protection, high current protectionSize (L x W x H ): Approx. 73 x 60 x 27 mmMaterial: Plastic, metalPackage Including:1 x RioRand Speed Controller