Abstract: Synchronizing device in a motor vehicle gearbox, comprising a synchronizer hub (1), an engaging sleeve (2) non-rotatably but axially displaceably mounted on the hub, an outer and an inner synchronizing ring (8a, 13) on one side of the hub and a single synchronizing ring (8b) on the other side of the hub. The engaging sleeve has first, and second groups of internal teeth (4a, 4b), each group being divided into three sets of teeth and each set in one group adjoining a set in the other group. The outer synchronizing ring has three sets of blocker teeth (9a) facing the engaging sleeve teeth (4a) of the sets of the first group and lacks teeth in intermediate areas (19a), while said single synchronizing ring (8b) has three sets of blocker teeth (9b) facing the engaging sleeve teeth (4b) of the sets of the second group and lack teeth in intermediate areas (19b).