- The S type is applied when there is no possibility to install an additional gearbox in the middle of the power base unit, like the B type. It installs a bearing unit in the middle of the shaft to prevent shaft deflection and can extend the lifespan of the ball bearings inserted inside the gearbox.

- The B type has a gearbox installed in the center, which helps prevent deflection of the upper frame. However, since the S type only addresses shaft deflection, the upper frame's deflection must be considered during the design when using the S type.