Fangrui Product Details Features: Stop Fluctuation Of Voltage, Automatically Maintaining Generator Output Terminal Voltage At A Set Value. Prevent Generator From Suffering Damages Of Voltage Fluctuation Or Over Load. It Uses An Electromechanical Mechanism, Or Passive Or Active Electronic Components. According To The Design, Which Is Used To Manage One Or More Ac Or Dc Voltage. In Addition To The Shunt Regulator, The Regulator Operates Through A Number Of Fixed Internal Comparison Of The Actual Output Voltage Of The Reference Voltage. Any Differences Are Used To Control The Zoom And Regulatory Elements. Color: Black Material: Plastic Package Contents: 1 X Voltage Regulator Only The Above Package Content, Other Products Are Not Included. Note: Light Reflection And Different Displays May Cause The Color Of The Item In The Picture A Little Different From The Real Thing. The Measurement Allowed Error Is +/- 1-3cm.