a 78 g of b d accessory 46 meets the requirement that it have an irregular profile and further satisfies the strong preference for a rib which has a variable height relative to the axial centerline of the elastomeric accessory component 66 in particular each of the ribs 78 a 78 g varies in height from a minimum height h 1 relative to the axial centerline 65 of the b d accessory 46 to a maximum height h 2 relative to that centerline see fig6 as discussed above this produces an inner rib region 95 c and outer rib regions such as 95 d fig6 which are relatively stiff and flexible respectively which have different sizes and shapes and which therefore provide optimal multimode dampening of high frequency and low frequency vibrations while equiangular spacing of the scallops is employed in representative b d accessory 46 and while all of the scallops are of the same size and shape as are the ribs except for thickness this is not a requirement of the invention variations such as ribs of different sizes and shapes and or scallops which likewise vary in size and or shape and or are spaced at other than equiangular distances may equally well be employed in other embodiments of the present invention also as stated above cutouts of any other appropriate shape may be employed instead of scallops as shown fig3 the head 90 of representative elastomeric component end member 88 and the frustoconical end member 87 of that component also have symmetric cruciform configurations of the same character as ribs 78 a 78 g reference characters 96 and 98 in fig3 identify a convex.