Cylinder rings having single-start nut and bolt threads matched to one another and axial stop surfaces, running perpendicularly to the cylinder axis, between the cylinder rings are distinguished by the fact that the stop surfaces (11, 12) assigned to the nut thread (3) and the bolt thread (4) extend in an axially rising manner over at most one thread turn and each have at the end a step surface (13, 14) between the axially offset stop planes of the stop surfaces (13, 14).