relatively large radius is approximately 0 5 inch radius according to this arrangement a gently sloping ramp surface 74 provides an easy transition for the preloaded upper end seal element 30a to be deflected onto the radially offset prop surface 64 as the slope angle is increased it becomes more important to radius the corners of the transition and the specific radius values are determined based primarily on the size of the packer as shown in fig2 a the upper outside seal element 30a has a substantially shorter longitudinal dimension than the central seal element 30b and the lower outside seal element 30c the longitudinal dimension of the prop surface 64 is selected so that the upper outside seal element 30a is fully supported and the central seal element 30b is at least partially supported on the radially offset prop surface 64 in the set expanded position as shown in fig3 a even though the lower outside seal element 30c and the central seal element 30b may be subjected to longitudinal excursions as a result of pressure fluctuations the sealing engagement of the upper outside seal element 30a is maintained at all times the lower and upper outside seal elements are reinforced with metal backup shoe 70 and 56 respectively the metal backup.