single piece of material and has a bore 142 formed along its central axis the top lobe 132 and the bottom lobe 138 are of similar proportions diameter and radius while the intermediate lobe 136 is smaller thus a u201c bow tie u201d shape is presented advantages have been discovered incident to the use of a bow tie profiled roller 114 over the more conventional u201c barrel u201d shaped roller not shown the bow tie shape allows for a narrower point of contact between the roller surface 114 and the tubular 202 to be expanded in this respect less force is required to expand a tubular 202 at a single radial point than over an extended surface area this in turn facilitates the transition within the tubular 202 from elastic deformation to plastic deformation thus a tighter seal can be accomplished the bow tie profile further allows for two separate points of radial contact an upper 132 and lower 138 point thereby doubling the seal contact points 402 406 the intermediate roller point 136 aids further in the expansion of the tubular 202 while the preferred embodiment for expansion of the tubular body 202 employs rollers 114 having a bow tie profile it is understood that other profiles may be employed for rollers 114 it is within the scope of this invention to utilize other roller shapes such as a u201c barrel u201d.