Feature: Overcurrent protection: The motor speed controllers comes with a 2A fuses. When the current is too large, the fuses is blown, and it will be automatically reconnected after the fuses is blown. Potentiometer function: The motor speed controllers has an external potentiometer, which has the function of speed regulation, but does not have a switches. Voltages and current:Input voltages: 1.8/3/5/6/12VCurrent: less than 2A.Please connect to direct current, do not connect to 220V alternating current. Note: Before trying to connect the controllers, make sure it power is off if you want to change the direction of the motor, replace the positive and negative cable of the motor. What it does: This motor speed controllers helps you control the speed of a motor by setting pulse width modulation (PWM). Specification: Material:Plastic Line Length:Approx.20cm/7.87 Size:Approx.32x32mm/1.25x1.25 Note: Please allow 1-2cm errors due to manual measurement,Please make sure that you do not mind before you order. Due to the difference between different monitors, the picture may not reflect the actual color of the item. Package includes: 4Pcs/set PWM Controllers