design provides a positive applied force to the opposed segments through an opening in the segments to move them relatively to each other to the smaller diameter position the use of angled flats toward which the segment noses move creates a very small clearance adjacent a sealing element that is located between the flat ends of the oppositely oriented segments that sit against a radial surface as a result going around for 360 degrees there is either no place for the seal material to be extruded or there is an array of segment noses with undercuts that run parallel to a tapered flat on the mandrel portion to present a very small clearance that has the effect of retaining the seal material against extrusion the nose are made or machined to a rounded shape so that even if they abut the end of a sealing element there will not be damage or any tearing of the sealing element while the preferred placement of the backup assembly is between sealing elements other arrangements can be used such as putting the backup assembly on one or both ends of a sealing element and in a position of exposure to well pressures and fluids the segments in the ring or rings that make up the backup assembly used in these locations can also be equipped with wickers and perform a double duty as a backup assembly providing circumferential anti extrusion protection for an adjacent sealing element as well as an anchor for that tool other tools that need a backup or protection from extrusion of components when subjected to well pressure when set are also contemplated to.