brand new and high quality Input voltage range:4-40VDC Output voltage range:1.25-37DC adjustable Output current:2A Voltmeter range:0 to 40V,error +-0.1V Input reverse polarity protection Built in output short for protection function Built in thermal shut dowen function L x for W x H=6.1 x 3.4 x12cm(approx.) LED digital voltmeter tube,the accuracy is adjustable function,can be aimed at your multimeter adjustable accurate Press the right for key to let the dispaly show the input or output voltage.when the right" OUT" led light,it shows output,the left "in" led show input Quantity:1PC How to adjust the accuracy? Output voltage calibration steps Step 1, adjust the right button so that "OUT" LED lighted, the voltmeter shows the value of output voltage; Press the right button for more than 2 seconds, release, voltmeter and "OUT" LED flashes in synchronization so that you enter the output voltage calibration mode. Step 2,press the right button (normal speed), the voltage value is adding up a unit; Press the left button, minus a unit; Due to a unit is less than 0.1V, the minimum voltage display to 0.1V, so you need to continuously press 1-5 times to see the voltmeter change 0.1V, how many times voltmeter change 0.1V by pressing the for key, depending on the current display voltage, the higher the voltage, the fewer the number of press. Step 3,press the right button for more than 2 seconds, release, to exit the output voltage calibration mode. All parameters set to automatically power down to save. Input voltage calibration steps Step 1, adjust the right button so that "IN" LED lighted, the voltmeter shows the value of input voltage; press the right button for more than 2 seconds, release, voltmeter and "IN" LED flashes in synchronization so that you enter the input voltage calibration mode. Steps 2 and 3, consistent with the output voltage calibration method. Note Some customers report: "The module can not be adjusted, the output voltage is for always equal to the input voltage." When you encounter this problem, please counterclockwise rotation of the potentiometer 10 laps or more, then you can adjust the output voltage. Because the factory default output voltage is 20V.