The magnetic or mechanical treadmill are not equipped with engine and do not need electric current magnetic treadmills .
They are usable only for walking and not for running as the belt turns thanks to the push of the feet.
The running plane must necessarily be inclined (otherwise it would not slip on the flat).
The interesting aspect of the magnetic treadmill is in the price, as they are inexpensive products and in the smallest footprint compared to an electric or motorized treadmill.
Magnetic treadmills do not have running surface cushioning systems.
The physical exercise carried out on these mats is much more tiring than a traditional treadmill as the thrust of the legs on the belt and the not completely correct posture caused by an uphill walk do not facilitate the gesture of walking.
As for the technical data of the magnetic treadmill I would not give much importance to the number of flywheels (one or two) and their weight (5, 7 kg etc.)
My advice remains to buy a treadmill with an engine so that you can walk on the flat and with an upright posture and why not even run.