As they do so, each pair applies pressure to a soft ring around the driveshaft. The pulsating muscles collectively and continuously pinch the shaft and apply a rotational force, causing it to turn.

Generally speaking, hollow shaft type of small volume, but the amount of magnetic force (magnetic power) also stretch out shaft type than for small.

In contrast, in the outstretched shaft type clutch or brake, magnetic coil and transmission between units have small desert land idle, so demand greater magnetized force.