Features: Can be directly connected to the stepping motor, no external driver. High precision, adjustable speed, Angle can be set, and the speed can be real-time displayed. Speed controller is made with high quality circuit board which ensures a longer service life. This simple and easy-to-use DC motor speed controller has an stable performance. Designed with a digital display that shows the rate in percent of actual speed to maximum speed. Specification:Condition: 100% brand newModel: YF-20Control voltage: 7~30VCurrent: within 2AStepper motor: common 42,57 two-phase four-wire five-wire six-wire stepper motorSpeed description: real-time speed regulation: 0.1~999 RPM; (most 42,57 stepper motors have a maximum speed of about 350 RPM)Angle: 1~9999 degrees can be set; 360 degrees in a circle; Users can convert their own needs to run distancePackage List:1 * Speed Controller