the lock ring 250 prevents movement of the lower piston 200 in an opposite direction the sealing element 300 is an annular member disposed about the body 102 between the lower piston 200 and the shoulder 400 the sealing element 300 may have any number of configurations to effectively seal the annulus created between the body 102 and a tubular there around for example the sealing element 300 may include grooves ridges indentations or protrusions designed to allow the sealing element 300 to conform to variations in the shape of the interior of the tubular the sealing element 300 can be constructed of any expandable or otherwise malleable material which creates a set position and stabilizes the body 102 relative to the tubular and which a differential force between the bore 103 of the body 102 and the wellbore does not cause the sealing element 300 to relax or shrink over time due to tool movement or thermal fluctuations within the wellbore for example the sealing member 300 may be a metal a plastic an elastomer or a combination thereof the shoulder 400 is an annular member disposed about a lower portion of the body 102 and adjacent a lower portion of the sealing element 300 in the preferred embodiment the shoulder is a releasable shoulder and includes a first 402 and second section 404 the first section 402 is offset from the second section 404 thereby forming a cavity 415 between an.