The rotary actuators of the series HSE fulfil the function of an end position damping in addition with, respectively without, adjustable rotating angle limitation. This means the deceleration, the delay of the angular movement up to standstill. For the damping the cross section of the bore for the medium draining off is progressively reduced and thus the moved masses are hydraulically stopped. The end position has been attained when the bore is completely closed and the medium can no longer drain off.