The present invention refers to a seal ring for a mechanical seal, comprising: a base body (2) with a diamond layer (3) which is applied to the base body (2) and configured as a sliding surface, wherein the diamond layer (3) has a thickness (D) which is less than or equal to 4 μm, particularly less than or equal to 3 μm, particularly less than or equal to 2 μm, particularly preferably about 1 μm, and wherein the base body (2) is without fissures or only comprises fissures that have a maximum longitudinal extension (L) on a surface of the base body (2) or in the base body (2) that is less than or equal to 5 μm.