Piston stroke pipette with a drive unit, and with a displacement unit which is mounted on the drive unit and which has a piston drive for at least one piston, wherein the displacement unit is dismountable from the drive unit, wherein the drive unit has an actuating drive for the piston drive and a receiving portion for the displacement unit, wherein the displacement unit has a fastening portion which fits the receiving portion of the drive unit, wherein a first detachable mechanical connection is provided between the actuating drive and the piston drive, and a second detachable mechanical connection is provided between the receiving portion of the drive unit and the fastening portion of the displacement unit, and wherein at least the second detachable mechanical connection is configured as a magnetic connection, characterized in that a mechanical means is provided for separating and coupling the magnetic connection between the receiving portion and the fastening portion, and - in that the mechanical means has a lever which - is supported on the drive unit with a fulcrum and, when manually actuated, acts on the displacement unit and thereby separates the magnetic connection, or - is supported on the displacement unit with a fulcrum and, when manually actuated, acts on the drive unit and thereby separates the magnetic connection, or - in that the mechanical means has an axially profiled cam disc and a cam guide which is congruent to the cam disc, and in that the magnetic connection is separable by a rotary movement of the cam disc and the cam guide relative to each other, or - the receiving portion of the drive unit and the fastening portion of the displacement unit each have at least one magnetic means (16'; 17) of the magnetic connection, in that at least the magnetic means (16'; 17) of the magnetic connection are rotatable relative to each other when the magnetic connection is closed, and in that the magnetic means (16'; 17), in a first rotary position, are opposite and congruent to each other and active and, in a second rotary position, are non-congruent and thus inactive or substantially inactive, and in that the mechanical means - is a holder (24', 27) for the magnetic means on the displacement unit, which holder (24', 27) is rotatable together with the magnetic means relative to the magnetic means on the drive unit, or - is a holder for the magnetic means on the drive unit, which holder is rotatable together with the magnetic means relative to the magnetic means on the displacement unit. - in that the mechanical means has a lever which - is supported on the drive unit with a fulcrum and, when manually actuated, acts on the displacement unit and thereby separates the magnetic connection, or - is supported on the displacement unit with a fulcrum and, when manually actuated, acts on the drive unit and thereby separates the magnetic connection, or - is supported on the drive unit with a fulcrum and, when manually actuated, acts on the displacement unit and thereby separates the magnetic connection, or - is supported on the displacement unit with a fulcrum and, when manually actuated, acts on the drive unit and thereby separates the magnetic connection, or - in that the mechanical means has an axially profiled cam disc and a cam guide which is congruent to the cam disc, and in that the magnetic connection is separable by a rotary movement of the cam disc and the cam guide relative to each other, or - the receiving portion of the drive unit and the fastening portion of the displacement unit each have at least one magnetic means (16'; 17) of the magnetic connection, in that at least the magnetic means (16'; 17) of the magnetic connection are rotatable relative to each other when the magnetic connection is closed, and in that the magnetic means (16'; 17), in a first rotary position, are opposite and congruent to each other and active and, in a second rotary position, are non-congruent and thus inactive or substantially inactive, and in that the mechanical means - is a holder (24', 27) for the magnetic means on the displacement unit, which holder (24', 27) is rotatable together with the magnetic means relative to the magnetic means on the drive unit, or - is a holder for the magnetic means on the drive unit, which holder is rotatable together with the magnetic means relative to the magnetic means on the displacement unit. - is a holder (24', 27) for the magnetic means on the displacement unit, which holder (24', 27) is rotatable together with the magnetic means relative to the magnetic means on the drive unit, or - is a holder for the magnetic means on the drive unit, which holder is rotatable together with the magnetic means relative to the magnetic means on the displacement unit.