This is a very compact hydraulic tunnel thruster.
The hydraulic motor is inside the lower bulb housing, and is directly connected to the propeller shaft.
These are made of steel, and are fairly simple build, no driving gears sets and only a few bearings inside, for easy repair and very little maintenance.
The bulb is the heart of the thruster and is simple to dismantle from the support.
There is very little space needed inside the vessel as no hydraulic motor or electric motor on top.
The system is very fast reversible because of the hydraulic system.