as seen in fig2 however when the packer is partly closed as in fig2 shoulders 120 on plates 44a engage shoulder structure 121 limiting further inward displacement of inserts 30a while shoulders 122 are not yet engaged against shoulder structure 121 this condition may for example correspond to fig6 a as described above subsequently as the packer is further constricted inserts 32a move inwardly until shoulders 122 engage shoulder structure 121 as seen in fig2 after which the packer rubber external to the inserts 32a may be even further inwardly displaced to cause seal off against the pipe 19 with greater pressure the webs 31 and 33 acting as fixed anchors for such rubber in fig2 inserts 30b and 32b correspond to inserts 30 and 32 respectively excepting that inner edge portions of webs 31b associated with inserts 30b are located further from axis 40 than the inner edge portions of webs 33b associated with inserts 32b this is opposite from the construction of fig2 and fig3 as a result the folds 140 of rubber being extruded inwardly toward the pipe 19 have convex forward edges 141 with cusps 142 proximate the interengaged edges 47b of plates 44b further while this will produce folds of extruded rubber similar to those of fig4 and 5 the location of the cusps of fig4 straddle the junctions 47 of plates 50 while the cusps of fig2 are at the junction 47b of plates 44b when the cusps are in.