Piston cylinder unit

The cylinder unit (10) has a cylinder (11) whose one side is provided with a hydraulic pressure lubricant to lubricate a surface between the cylinder and a piston (15). A peripheral surface (23) of piston is extended in a direction of a longitudinal axis (21) to form a longitudinal recess (25). Other side of cylinder is provided with an entry region (28) of piston into a hole (13) formed in cylinder. The entry region in operational position of piston is hydraulically separated from one side of cylinder, and spaced away from an end region (27) of recess.