A well tool for applying a pulling or a pushing force to an object in an interior of a well bore comprising: a) an inner member comprising a first elongated member, a second elongated member and an actuation means axially interconnecting the first elongated member and the second elongated member; b) an outer elongated member longitudinally moveably engaged with the inner member; c) a first seal defined between the first elongated member and the outer elongated member; d) a second seal defined between the second elongated member and the outer elongated member; e) a first piston area defined at a first end portion of the outer elongated member between an outer diameter of the outer elongated member and a sealed outer diameter of the first elongated member; f) a second piston area defined at a second end portion of the outer elongated member between the outer diameter of the outer elongated member and a sealed outer diameter of the second elongated member; and g) a sealed chamber defined between the first seal and the second seal, the sealed chamber including a fluid at a fluid pressure; wherein operation of the actuation means axially reversibly moves the outer elongated member relative the inner member while the fluid pressure remains constant; and wherein the first piston area and the second piston area are substantially equal and external pressure acting on these two piston areas, generates two opposing forces substantially balanced during relative movement.