HB4GL, 4″ hub motor, the smallest motor we have now, only 1.3kg. It is 150w, GEARLESS, DC brushless motor speed range from 10 km/h to 25 km/h
Dropout size 60mm. If you need a controller with this motor, you could have a try this one https://www.uumotor.com/4-inch-hub-motor-and-controller-scooter-kit.html
The standard version 24v 120w, 15km/h, 36v 150w,20km/h, if you need a different speed, we can customize it for you. Here is HB4GL 36v testing data
Can this small 4 inch motor be made in mono shaft version? Yes, it can.