Abstract: A synchronization unit of a switchable gear changing transmission for a vehicle. The synchronization unit includes a friction ring having an outer installation surface and a synchronizer ring having an inner installation surface. The outer installation surface of the friction ring is shaped as a first geometrically structured profile. The inner installation surface of the synchronizer ring is shaped as a corresponding second geometrically structured profile. The first profile of the friction ring is configured to engage with the second profile of the synchronizer ring in such a manner that the friction ring is secured in the radial direction to the axis and in the circumferential direction at the synchronizer ring.