compared with some of the synthetic rubbers which exhibit a marked increase in shear modulus with comparable decreases in temperature since natural rubber is less ozone resistant and more prone to deterioration from weathering a protective sheath 28 fig1 8 may be provided which is bonded to surface 24 the preferred material for sheath 20 is neoprene selected for its superior ozone and weathering resistance other protective materials may be provided however such as certain grades of butyl rubbers ehtylene polypropylene rubbers polysulfide rubbers silicone rubber and the like as dictated by effectiveness vs price the embodiment of fig5 is illustrated as being provided with three rings 18 disposed in both vertically spaced apart and laterally offset relation as shown however it is evident that the benefits of this invention may be attained by providing two or more of such rings disposed in vertically spaced apart and laterally offset or staggered relation the number provided being dependent upon the cross sectional diameters of each ring the expected rotational and lateral movement to be imposed on body 16 the shape factor desired and related loading conditions fig6 illustrates an alternate embodiment of the structure shown in fig2 and 5 in this embodiment the peripheral edge 24 is provided perpendicular to the surfaces 20 and 22 three rings 18 are disposed in.