For Hidoes B6/B10 Controller, 
The maximum adjustable speed is: 28mph

The product content of this link:

1X  controller

Note: This product is not a quality issue and cannot be returned. It is only for after-sales repair. Friends who need it, please read it carefully before purchasing. Thank you!

The shipping carrier is: Orange Link Express

The delivery time is 3 working days and the transportation time is 5-7 days