Abstract: A piston for a cylinder, in particular for a hydraulic piston storage or a hydraulic cylinder having a multipart configuration with two piston parts (11) made of material nontransformable under pressure, subjected to the pressure prevailing in the cylinder, which piston parts comprise, between them, a radially expandable sealing member, with the piston parts (11) arranged such that the pressure in the cylinder axially acting on them effects an increase in the pressure of partial areas of the sealing member against the cylinder wall, wherein the sealing member is made of a support part (12) consisting of the deformable material for a piston seal (20) and at least one piston seal (20) inserted in a groove (19) formed on an outer circumferential surface of the support part (12), and that the cylindrical support part (12) has tapers (13) on both sides with across-piece (14) remaining between them for accepting the two engaging piston parts (11) in such a way that the support part (12) overlaps the piston parts (1