Synchronizer unit for a manual transmission which comprises at least one shaft rotatable about an axis and at least one first loose wheel seated on the shaft and having a clutch body which has a friction surface, the synchronizer unit being equipped with - a hub which is seated fixed in terms of rotation on the shaft when the synchronizer unit is in the installation position; - a synchronizing ring which is rotatable to a limited extent in relation to the hub and which has at least one stop boss (34, 34a) and a friction surface which can be pressed axially against the friction surface of the clutch body of the first loose wheel, - a sliding sleeve which is connected axially displaceably and fixedly in terms of rotation to the hub and which has on a circumferential inner face a contact surface and a toothing, - a first lever which is arranged in the hub and has at least one lever end (51, 52) and a lever head, the lever head bearing against the contact surface at least in specific axial positions of the sliding sleeve, the contact surface and the lever head being designed in such a way that a force acting upon the sliding sleeve acts in a first axial direction which presses the lever head in the axial direction and in the radial direction; the lever, as a result of the axial pressure on the lever head, pressing against the synchronizing ring which, in turn, presses with its friction surface against the friction surface of the clutch body, as a result of which, in so far as the rotational speeds of the synchronizing ring and of the clutch body are not synchronized, a moment of friction acts upon the synchronizing ring; as a result of the moment of friction the synchronizing ring being rotated in the direction of a blocking position or assuming a blocking position in which the synchronizing ring is supported with the stop boss on the lever end (51, 52) in the circumferential direction, thus leading to a lever unblocking moment; the radial pressure on the lever head changing the position of the lever end (51, 52), the position of the stop boss, bearing against the lever end (51, 52), of the synchronizing ring and consequently the blocking position in the circumferential direction, characterized in that the synchronizing ring has a blocking toothing, the toothing of the sliding sleeve being capable of being brought into bearing contact with the blocking toothing in the blocking position of the synchronizing ring, as a result of which a toothing unblocking moment counteracting the moment of friction is generated. - a hub which is seated fixed in terms of rotation on the shaft when the synchronizer unit is in the installation position; - a synchronizing ring which is rotatable to a limited extent in relation to the hub and which has at least one stop boss (34, 34a) and a friction surface which can be pressed axially against the friction surface of the clutch body of the first loose wheel, - a sliding sleeve which is connected axially displaceably and fixedly in terms of rotation to the hub and which has on a circumferential inner face a contact surface and a toothing, - a first lever which is arranged in the hub and has at least one lever end (51, 52) and a lever head,