Check the listing for details. Bafang M300 / M400 / M420 EB357 SpeedBox Unlocking Kit 3.1. Condition: New. Listed at 208.56 USD. You can set the maximum speed of electrical assistance by changing three levels downwards and then three levels at the top. After, the current speed limit will appear on the screen. The maximum speed of electrical assistance can be changed by briefly pressing the Light button, or by turning the 360 degree rear wheel. The last displayed limit will be stored after five seconds of inactivity. You can set the Maximum Speed of the Electric Assistance by Changing the Mode Three Levels Down and then Three Levels Up. After that, The Current Speed Limit Will Signore on the Screen. The Maximum Speed of the Electric Assistance Can Be Changed by Briefly Pressing The Light Button, or by Touring The Rear Wheel 360 Degrees. The Last Limit Displayed Will Be Stored After Five Seconds of Inactivity.