flush with and above lowermost surface 46 0024 fig4 and 5 show gripper body assembly 20 is also an open right circular cylinder gripper body assembly 20 comprises a gripper element 54 and upper and lower support or reinforcing rings 56 58 gripper element 54 forms the cylindrical wall 60 of gripper body assembly 20 has upper and lower ends 62 64 respectively and is preferably made from a flexible durable elastomer such as urethane or treated natural rubber the elastomer used to form gripper element 54 is generally harder than the elastomer used to form bladder 22 rigid support rings 56 58 are molded into ends 62 64 respectively of gripper element 54 upper support ring 56 is embedded in but its upper surface is preferably flush with uppermost part of end 62 upper support ring 56 has internally threaded holes 66 similar to holes 38 of reinforcement rings 24 26 lower support ring 58 is preferably completely embedded in lower end 64 similar to reinforcement rings 24 26 support rings 56 58 provide structural rigidity to ends 62 64 of gripper element 54 thus the nominal diameter of gripper element 54 remains essentially constant in the vicinity of support rings 56 58 the diameter may vary however along the more central portion of gripper element 54 cylindrical wall 60 of gripper element 54 has a radially inner surface 68 and a radially outer surface 70 in its natural state outer surface 70 has a constant diameter just less than the nominal inner diameter of bladder 22 inner surface 68 of gripper element 54 is cylindrically symmetric but has a variable diameter even when wall 60 is in its natural state tracing the profile of inner surface.