A balancing piston for centrifugal compressors, to control and damp subsynchronous vibrations, comprises a cylindrical body (21) which is keyed onto the rotor (3) and a cylindrical structure which contains the body (21) on the stator side with interposition of a seal (16) with small cells wherein the play between the rotor(3) and the stator (2) increases in the direction of the flow of gas through the play.