The main hyperspace propulsion mechanism of the Millennium Falcon after it was improved from an Isu-Sim SSP05 hyperdrive generator was the Series 401 hyperdrive motivator.
While it was thought of as a "more efficient" piece of equipment, it seemingly possessed the same Hyperdrive Rating of 0.5 as the significantly altered SSP05, even though it is plausible that the drives were simply exchanged to return the Falcon to its original 0.5 rating by the conclusion of the Black Fleet Crisis.