damper body tube 14 slides over flux ring 58 mr fluid does not leak past the flux ring 58 the mr fluid within damper body tube 32 is a conventional mr fluid that has magnetic particles such as iron or iron alloys the magnetic particles are controllably suspended within the fluid by controlling a magnetic field through the flow gap 60 thus a desired damping effect between the sprung and unsprung masses of the vehicle is achieved by controlling the application of an electric current to coil 50 in order to vary the magnetic field and hence the flow characteristics of the mr fluid in the flow gap 60 a gas cup 70 is also carried in the damper body tube 32 between the piston assembly and the end the gas cup 70 carries a dynamic seal 72 and slides along the inner surface 68 of damper body tube 32 separating a compensation chamber 74 from the compression chamber 64 while the extension chamber 66 and compression chamber 64 carry a supply of mr fluid the compensation chamber 74 carries a compressible nitrogen gas supply during extension and compression directed travel of the damper body tube 32 relative to the piston assembly 28 a decreasing or an increasing volume of the piston rod 30 is contained within the damper body tube 32 depending on the stroke position of the strut 10 in order to compensate for this varying volumetric amount of the piston rod 30 within the fluid filled chambers 64 66 the gas cup 70 slides compressing or expanding the compensation chamber 74 the predominate means of supporting the damper body tube 32 within the housing tube 14.