Provided is a synchronizer device and method for a manual transmission, having a sliding sleeve which includes an internal toothing having sliding sleeve teeth, a clutch body, the clutch body having an external toothing having a multitude of clutch body teeth for internal toothing of the sliding sleeve to engage therein, and a synchronizer unit. The clutch body teeth at the axial tooth ends adjacent the sliding sleeve and/or at least some of the sliding sleeve teeth at the axial tooth ends adjacent the clutch body each include at least one convex end face which extends in the circumferential direction from a root point adjacent to a tooth flank of the respective tooth via an axially protruding apex portion as far as to a root point adjoining an opposite tooth.