Updated: May 16, 2019
The hubs are fully sealed and self contained units, holding battery, motor and sensors. At the time of purchase they came set up for a single speed and my two are 120mm O.L.D. The one unique build stipulation is that the wheels are mounted in long horizontal dropouts. This satisfies two needs, the first gives room to fit the bevelled locking plates to manage the power as it is put down, the second guarantees the axle is held flat. This is important, the unit has a tilt sensor which needs to be held horizontally so it knows when you are climbing a hill and respond accordingly.
(Image taken from Zehus Website)
These track dropouts gave my what I needed with a couple of alterations.
It's all very well saving on weight, but I wanted to fit a screw there. I also removed the beefed up edge on the outer side of each dropout so that the plates would mount flush.