There's no real width saving for parking, maybe a couple of inches at best on either side. The supporting arms do not fold - only the mirror housing rotates inward. I think the main benefit is that it turns the mirror face towards the car, making it slightly less likely to get clipped or sideswiped. Also, you won't return to find a lady of the night using it to fix her lipstick.
Hope these pics illustrate, sorry for the poor lighting as it is evening already.
Hope these pics illustrate, sorry for the poor lighting as it is evening already.