The most compact type with a straight cylindrical spline nut. When transmitting a torque, a key is driven into the body.
The spline nut can be attached to the housing via the flange, making assembly simple.
It is optimal for locations where the housing may be deformed if a keyway is machined on its surface, and where the housing width is small.
Since it allows a dowel pin to be driven into the flange, angular backlash occurring in the fitting can completely be eliminated.