Control valve for a device, in particular for a hydraulic control device, for variably setting the control times of gas exchange valves in internal combustion engines, including a housing component, a control piston and a retaining ring, the control piston being movably mounted, loaded by a spring, on the one hand, and limited with the aid of the retaining ring, on the other hand, the retaining ring projecting over the control piston in the radial direction and being fixable in the axial direction in a recess in the housing component, and a control sleeve and a plastic shell surrounding the control sleeve being provided between the control piston and the housing component, and the retaining ring being axially attachable to the plastic shell in addition to being fixable to the housing component, and limiting the movement of the control piston and/or the control sleeve.