Abstract: An actuator for a vehicle suspension system comprises a first member connectable to one of a sprung mass and an unsprung mass of the vehicle. The first member has an opening with an inside wall of predetermined dimension. A second member is connectable to the other of the sprung mass and the unsprung mass of the vehicle. The second member has an outside wall of a predetermined dimension. The dimension of the outside wall of the second member is adapted so as to be telescopically received within the opening of the first member thereby defining a fluid chamber. A source of pressurized fluid is connectable to the fluid chamber. A fluid seal is located near an end of the first member form a fluid seal between the first member and the second member.