12v-40v 10a Pwm Dc Motor Speed Controller w/ Knob--high Efficiency, High Torque, Low Heat Generating with Reverse Polarity Protection, High Current Protection Operating voltage: DC 12V-40V PWM duty cycle: 10% -100% stepless From left to right they are Motor-, Motor+, Power-, Power+ PWM Frequency: 13 KHz Control Power: 0.01-400W